Sher Khan / EPA

Afghan police attend their graduation ceremony in volatile Helmand, Afghanistan, on Wednesday. International troops in the country have suspended their training program for Afghan security forces following a spate of attacks on foreign soldiers by Afghans in uniform.

KABUL, Afghanistan -- Hundreds of Afghan service members have been arrested and expelled after a string of rogue shootings killed dozens of NATO personnel, the country's Ministry of Defense said Wednesday. 

"Hundreds were sacked or detained after showing links with insurgents," ministry spokesman Zahir Azimi told reporters. "In some cases we had evidence against them, in others we were simply suspicious."  

Those arrested were thought to have ties to criminal elements and those expelled were deemed to have irregular paperwork, mental-health problems or false documentation, Azimi told NBC News.

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.

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The move comes during the worst year for such insider, or "green-on-blue", attacks. At least 45 members of the NATO-led force have been killed by Afghans in uniform this year, including 15 in August alone. That compares with 35 killed in such attacks in all of 2011. 

US 'insider' killings mount in Afghanistan

The spike of insider attacks has sparked concerns that Afghan forces will not be capable of taking over security by 2014 as planned. 

Azimi told NBC News that his ministry started an investigation into the killings within the 195,000-strong Afghan army three or four months ago. 

But tensions are still simmering. The shooting dead of three Australian troops by an Afghan army sergeant in the south last week prompted a deadly raid to find the rogue soldier, causing a war of words between Canberra and Kabul.

U.S. forces in Afghanistan said on Sunday they had suspended training new recruits to the Afghan Local Police, a militia separate from the national police, following the spike in insider attacks.

Seventeen villagers beheaded in southern Afghanistan after 'music party'

And on Wednesday, NATO's top official told President Hamid Karzai  that he was deeply concerned about the surge in assaults by Afghan troops on their foreign allies.

Spokeswoman Carmen Romero said Karzai had assured Secretary-General Anders Fogh Rasmussen in a phone conversation that he was doing all he could to stop the attacks. 

U.S. Gen. John R. Allen, who commands NATO's 129,000-strong force, briefed the alliance's top decision-making body on Wednesday about the attacks, The Associated Press reported.

Reuters and The Associated Press contributed to this report. 

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KABUL, Afghanistan -- United States military officials have suspended the training of Afghan Local Police (ALP) in the wake of a deadly series of so-called ‘green on blue’ attacks by Afghan soldiers and police on their international allies.

In a statement late Saturday, Col. Thomas Collins, US Forces Afghanistan spokesperson, said the training has been put on hold in order to carry out intensified vetting procedures on new recruits, and 16,000 existing ALP recruits will be re-vetted.

“While we have full trust and confidence in our Afghan partners, we believe this is a necessary step to validate our vetting process and ensure the quality indicative of Afghan Local Police," he said in the statement.

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

Many of the 'insider' incidents might have been prevented if existing security measures had been applied correctly, according to the Washington Post which first reported the training suspension.

The newspaper said already-trained recruits would also be re-vetted.

"Current partnered operations have and will continue, even as we temporarily suspend training of about 1,000 new ALP recruits while re-vetting current members," said the statement. “Despite the recent rise in insider attacks, they are relatively rare."

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

Forty-five allied troops have been killed in 34 ‘insider’ attacks this year alone. The Afghan army is implicated in 19 of those attacks, but their training will not be halted.

Last week, an Afghan soldier shot and killed two American soldiers on Monday during a dispute in Laghman province in Afghanistan. 

Defense Secretary Leon Panetta called Afghan President Hamid Karzai on Aug 19 to express concern over the issue, urging him to work with U.S. commanders to ensure more rigorous vetting of Afghan recruits. Panetta’s intervention followed the 10th death of a U.S. service member at the hands of Afghan recruit in the space of just two weeks.

ALP training is a U.S. mission, carried out by Special Forces. Training of uniformed police and army personnel is done under the banner of the NATO operation.

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