An Afghan soldier shot and killed two American soldiers on Monday during a dispute in Laghman province in Afghanistan. The Afghan soldier was then shot and killed by U.S. forces.

"ISAF troops returned fire, killing the ANA (Afghan National Army) soldier who committed the attack,'' the NATO-led International Security Assistance Force said in a statement.

A senior military official in Kabul strongly disputes an Afghan military account which claims the two Americans were killed accidentally when the Afghan tripped on his weapon, which discharged and struck the U.S. servicemen. “The Afghan account is tortured beyond belief and total bull****,” the official told NBC News.

The deaths in Laghman brought the number of foreign soldiers killed this month to 12, prompting NATO to increase security against insider attacks, including requiring soldiers to carry loaded weapons at all times on base.

The deaths also come a week after U.S. Joint Chiefs of Staff chairman Martin Dempsey visited Kabul to talk about rogue shootings and urge Afghan officials to take tougher preventative action.

Taliban behead 17 civilians after 'late-night dance and music party'

There have been 33 insider attacks so far this year that have led to 42 coalition deaths. That is a sharp increase from 2011, when, during the whole year, 35 coalition troops were killed in such attacks, 24 of whom were American.

In all, 73 Americans have been killed by so-called “friendly forces” in the nearly 11-year war, with more than half occurring in the past eight months.

Afghanistan's government said on Wednesday it would re-examine the files of 350,000 soldiers and police to help curb rogue shootings of NATO personnel, but accused "foreign spies" of instigating the attacks.

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The killings, many of which have been claimed by the Taliban as evidence of insurgent reach and infiltration, have eroded trust between the NATO-Afghan allies and are complicating plans for transition to Afghan security within two years.

NATO commanders have played down the threat of infiltration, blaming most of the shootings on stress or personal differences between Afghans and their Western advisers that ended at the point of a gun, a frequent occurrence in Afghanistan.

But the U.S. general leading NATO forces in Afghanistan acknowledged last Thursday that the Taliban could be traced to more insider attacks than previously acknowledged, accounting for about a quarter of the cases.

US deaths in Afghanistan hit 2,000 in 'forgotten' war

The Afghan government agreed after Dempsey's visit to improve the vetting of army and police recruits by requiring stronger guarantors, a more stringent test questionnaire and biometric data on all would-be and existing personnel.

More undercover intelligence officers would be recruited and placed in Afghan security forces to keep an eye on soldiers and police, while security force members with families in neighboring countries would be heavily scrutinized for possible relations or exposure to cross-border insurgents.

But President Hamid Karzai's spokesman also said the number of attacks was also relatively small given the presence of 120,000 foreign troops among 350,000 Afghan security forces.

Reuters contributed to this report.

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KABUL, Afghanistan -- A man in an Afghan police uniform shot and killed a U.S. service member on Sunday, a U.S. Defense Department official said, raising the death toll to 10 in such attacks in the space of just two weeks.

The surge in violence by Afghan allies against their international partners has raised doubts about the ability of the two forces to work together at a key transition time. Afghan forces are expected to take over security for the country by the end of 2014, when the majority of international combat forces are scheduled to leave.

On the other side, a coalition airstrike killed dozens of Taliban militants, including one of their leaders, officials said.

The U.S. defense official in Washington discussed the matter on condition of anyonymity because the official notification process had not been completed.

On Saturday Defense Secretary Leon Panetta called Afghan President Hamid Karzai to encourage him to work with U.S. commanders to ensure more rigorous vetting of Afghan recruits.

Panetta also urged Karzai during the telephone call to work with NATO to boost counterintelligence efforts and speak more to village elders who have ties to the army and police, the Pentagon said in a statement.

"They expressed shared concern over this issue and agreed that American and Afghan officials should work even more closely together to minimize the potential" for future attacks, it added. 

Few details were immediately available about Sunday's killing of a coalition member in southern Afghanistan. NATO said only that they and Afghan authorities were investigating. Afghan officials could not be reached for comment.

What's leading Afghan troops to turn on coalition forces?

The Taliban have been actively recruiting members of the Afghan security forces, saying in a statement last week that they considered these turncoat attacks a major part of their strategy against international forces.

Once an anomaly, these attacks have been climbing in recent months. There have been 30 such attacks so far this year, up from 11 in 2011.

US forces in Afghanistan ordered to keep weapons loaded at all times

On Friday it was disclosed that U.S. troops have been ordered to carry loaded weapons at all times in Afghanistan, even when they are on their bases. The order was a precaution against such insider attacks.

Ramadan attacks
The monthlong Ramadan fasting period that ended Sunday has been particularly violent. The Eid al-Fitr holiday on Sunday continued the trend.

Insurgents killed two pairs of brothers with links to the government as well as three NATO service members in three separate attacks.

In the first attack, a bomb hidden in a cemetery in the southern province of Helmand killed a police chief and his brother who were visiting a family grave for the holiday.

Seven of the men's family members were wounded in the early-morning blast in the provincial capital of Lashkar Gah, said the Helmand deputy police chief, Ghulam Rabbani.

No one claimed responsibility, but the attack was consistent with the Taliban's strategy to target authorities and others who align themselves with the government or international forces.

The two men were brothers of a lawmaker for Helmand province, Abdulwadood Popal, who was not at the cemetery at the time of the blast. The family was visiting the grave after attending a morning prayer service for the holiday, which ends the month-long Ramadan fasting period.

Slideshow: Afghanistan: Nation at a crossroads

Hoshang Hashimi / AP

More than ten years after the beginning of the war, Afghanistan faces external pressure to reform as well as ongoing internal conflicts.

Launch slideshow

Later in the western Farah province, gunmen on a motorcycle opened fire on the car of an intelligence service official as he was driving home from a family visit, killing him and his brother, who worked for the customs service.

Another relative was wounded, provincial deputy police chief Ghulam Ghows Malyar said.

In central Afghanistan, three NATO service members were killed when a vehicle struck a roadside bomb, officials said. Bamiyan Gov. Habiba Sarabi said the blast went off in Kohmard district while the troops were out on patrol.

NATO forces confirmed that three coalition service members were killed in a bombing, but did not provide their nationalities or other details.

Taliban spokesman Zabiullah Mujahid claimed responsibility for the attack in a statement.

Including Sunday's deaths, at least 41 international troops have been killed so far this month in Afghanistan.

The Associated Press and Reuters contributed to this report.

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Waseem Naikzad / AFP - Getty Images

Afghan security force sit on top of a military vehicle in Laghman province Wednesday. US Defense Secretary Leon Panetta said on Tuesday he was very concerned about the rise in insider attacks on US and NATO troops, and the impact they are having on cooperation with Afghan allies.

News analysis

KABUL, Afghanistan – A group of U.S. Marines in Helmand province was invited to dinner by a local police commander and his men late last week.  A little after midnight, under the dark Afghan sky, the Marines left the police compound and were shot in the back as they walked away. Three were killed.

Last week, seven Americans lost their lives after Afghans they were working with turned their weapons on them.

The military is now designating these incidents in which Afghan troops turn on coalition counterparts as "insider attacks," (they were once called "green-on-blue" incidents) to account for the non-security personnel also involved in the assaults. 

Insider attacks are now at the highest level they have been since the start of the war.

Three US special ops troops killed, Afghan officials say 

In 2007 and 2008 there were four such attacks and four deaths.

So far this year, there have already been 29 incidents in which Afghans turned their weapons on their coalition partners, killing 37.  That’s compared with a total of 21 incidents, in which 35 were killed, in all of 2011. 

The spike has startled many and brought calls to find the catalyst for the deadly problem.

Jose Cabezas / AFP - Getty Images

Members of the Afghan National Army are helped by a US soldier as they participate in a map reading training session at Narizah base in Narizah, Khost Province, on August 12, 2012.

Who or what is to blame? 
One group that would seem like the obvious culprit is the Taliban. They have claimed to infiltrate the Afghan National Security Forces, consisting of both the military and police, to help kill NATO troops from the inside. 

Last year, the group called on more Afghans in uniform to join their cause and turn their weapons on the “foreign invaders” because of their access and proximity. 

NATO does not deny some of the attacks have been from Taliban insurgency infiltration – but they attribute the trend to more than that.

Seven American troops killed in Afghan chopper crash

“There was infiltration; that is correct, we can acknowledge that,” said Brig. Gen. Gunter Katz, spokesman for the NATO-led International Security Assistance Force based in Kabul.  However, he said most of the attacks could be blamed on more basic warfare issues.

“The main reasons for those green on blue incidents are personal grievances, stress situations and what we call battle fatigue,” Katz said.

Slideshow: Afghanistan: Nation at a crossroads

Hoshang Hashimi / AP

More than ten years after the beginning of the war, Afghanistan faces external pressure to reform as well as ongoing internal conflicts.

Launch slideshow

He attributes about 10 percent of the insider attacks to Taliban infiltration, and blames the remaining 90 percent on individual motives.

However, U.S. Defense Secretary Leon Panetta acknowledged the Taliban are somewhat to blame for the attack earlier this week.

“The reality is, the Taliban has not been able to regain any territory lost, so they’re resorting to these kinds of attacks to create havoc,” Panetta told reporters in a Pentagon briefing Tuesday, according to Stars and Stripes.

Panetta later said there is “no one source” responsible for the attacks, and that there are several reasons why Afghan forces would turn on coalition troops.

Cultural divide 
A former commander of the Afghan Border Police, Gen. Aminullah Amarkhil, blames the attacks on a disrespect of the Afghan culture by foreign forces.

“The main reason for these attacks is that the foreign troops have on many occasions humiliated the Afghan culture and religion,” Amarkhil said.  “They’ve entered Afghan homes without permission, killed innocent civilians, they’ve bombarded wedding parties, they’ve entered our mosques with dogs, burned the Holy Quran. All of these are the factors that have contributed to the Afghan army or police being infiltrated by people who have been humiliated by the foreign troops.”

The Afghan general admitted it is not just the fault of NATO, adding that the insider attacks are also because of the weakness in the Afghan National Security Forces’ recruitment system.

“We don’t have a proper procedure for recruitment in our army or police. There are people in the Afghan army who have come from Pakistan and have made Afghan identity cards, " said Amarkhil, explaining that loyalties can be divided.

Training on Afghan culture
Amarkhil believes more should be done to show respect for the Afghan culture and religion by the foreign forces. And ISAF says they are doing just that.

“We continue to improve this process further and further in order to teach our guys [about] ‘what is Afghan culture.’  What can be done, what must not be done,” Katz said.  “We are very serious about that.”

In the meantime, ISAF has implemented force protection measures to help prevent more insider attacks.  Katz would not elaborate on what those measures are.

“We permanently assess the environment our soldiers are working in and assess if the current force protection measures are still in accordance to our assessment. And if not, we change them.”

But Katz says that these incidents, although tragic, are isolated.

“We had a very bad week last week,” he says.  But he believes for the most part there is trust between the Afghan and international forces.

“The more we fight together, the more we trust each other.”

NBC’s Fazl Ahad contributed to this report.

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Updated at 12:35 p.m. ET: KABUL, Afghanistan -- A man wearing an Afghan army uniform shot and killed three American Marines, the U.S. military command said Friday. Afghan officials said the victims were American special operations forces troops.

Reuters reported that an Afghan police commander opened fire on the service members after inviting them to a meeting to discuss security. A U.S. military official confirmed the three deaths and said another service member had been injured during the incident.

NBC News' Jim Miklaszewski reported that a "lone gunman" remained on the loose and was being hunted. U.S. military officials said all of the American victims were Marines.

Citing Afghan officials, Reuters said the American special operations forces members were killed late Thursday while attending a meeting in the Sarwan Qala area, in what appeared to be a planned attack by rogue Afghan forces.

"The commander was Afghan National Police in charge of local police in Sangin," a senior Afghan official told Reuters on condition of anonymity. Sangin is a district of Helmand province.

"It looks like he had drawn up a plan to kill them previously," the official added.

A military official told NBC News' Courtney Kube that it was unclear whether the gunman was a member of the Afghan security forces or whether he was just wearing a uniform.

Taliban spokesman Qari Yousef Ahmadi told The Associated Press by telephone that the attacker, whom he identified as a member of Helmand police named Asadullah, had been helping U.S. forces train Afghan local police troops. However, the Taliban has made false claims about the details of attacks in the past.

The attack is the third killing this week of coalition soldiers by Afghans who are training to take over responsibility for security once most international forces leave in 2014.

So-called "green on blue" shootings, in which Afghan police or soldiers turn their guns on their Western mentors, have seriously eroded trust between the allies.

According to NATO, there have been 24 such attacks on foreign troops since January in which 28 people have been killed. Last year, there were 21 attacks in which 35 people were killed.

Senior Army leader slain
Earlier, the Pentagon confirmed that three U.S. service members -- including a senior Army leader -- and an American aid worker were killed Wednesday by a suicide bomber in Kunar province.

The victims included Command Sgt. Maj. Kevin J. Griffin, the most senior enlisted soldier for the 4th Brigade Combat Team, 4th Infantry Division. Griffin, 45, of Riverton, Wyo., was a Bronze Star recipient who first enlisted in the Army in 1988.

Maj. Thomas E. Kennedy, 35, of West Point, N.Y., and Air Force Maj. Walter D. Gray, 38, of Conyers, Ga., were also killed. USAID foreign service officer Ragaei Abdelfattah was identified as the other victim.

On Tuesday, two gunmen wearing Afghan army uniforms killed a U.S. soldier and wounded two others in Paktia province in the east.

And on Thursday, two Afghan soldiers tried to gun down a group of NATO troops outside a military base in eastern Afghanistan. No international forces were killed, but one of the attackers was killed as NATO forces shot back.

NBC News' Courtney Kube, Jim Miklaszewski and Atia Abawi, The Associated Press and Reuters contributed to this report.

Slideshow: Afghanistan: Nation at a crossroads

Ahmad Jamshid / AP

More than ten years after the beginning of the war, Afghanistan faces external pressure to reform as well as ongoing internal conflicts.

Launch slideshow

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