Updated at 6:46 p.m. ET: The United Nations Security Council on Thursday condemned a mortar attack by Syria on a Turkish border town that killed five people and demanded that "such violations of international law stop immediately and are not repeated.''

 “The members of the Security Council condemned in the strongest terms the shelling by the Syrian armed forces of the Turkish town of Akcakale, which resulted in the deaths of five civilians, all of whom were women and children, as well as a number of injuries. The members of the Security Council expressed their sincere condolences to the families of the victims and to the Government and people of Turkey,” the Security Council said in a statement.

“The members of the Security Council underscored that this incident highlighted the grave impact the crisis in Syria has on the security of its neighbors and on regional peace and stability. The members of the Council demanded that such violations of international law stop immediately and are not repeated. The members of the Security Council called on the Syrian Government to fully respect the sovereignty and territorial integrity of its neighbors.”

 The mortar attack happened on Wednesday and Turkey responded by striking targets in Syria later the same day and Thursday.

Seeking to unwind the most serious cross-border escalation in its 18-month-old crackdown on dissent, Damascus apologized through the United Nations for the shelling and said it would not happen again, Turkish Deputy Prime Minister Besir Atalay said. 

Syria's staunch ally Russia said it had received assurances from Damascus that the mortar strike was a tragic accident.

But Turkey's government said "aggressive action" against its territory by Syria's military had become a serious threat to its national security and parliament approved the deployment of Turkish troops beyond its borders if needed.

"Turkey has no interest in a war with Syria. But Turkey is capable of protecting its borders and will retaliate when necessary," Ibrahim Kalin, a senior adviser to Prime Minister Tayyip Erdogan, said on his Twitter account.

"Political, diplomatic initiatives will continue," he said.

Esber Ayayadin / Anadolu Agency via EPA

Turkish soldiers and relatives of Gulsen Ozer, who was killed by a mortar bomb from Syria, attend her funeral in Turkey's southeastern border region of Akcakale, Sanliurfa, Turkey, on Thursday.

Turkey hit back after a mortar hit a residential neighborhood in Akcakale on Wednesday, killing a woman, her three daughters and another woman.

The Syrian Observatory for Human Rights said several Syrian soldiers were killed in the Turkish retaliatory bombardment of a military post near Tel Abyad, a few miles across the frontier from Akcakale. It did not say how many soldiers died.

"We know that they have suffered losses," a Turkish security source told Reuters, without giving further details.

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NATO said it stood by member nation Turkey and urged Syria to put an end to "flagrant violations of international law."

The U.S.-led Western military alliance held an urgent late-night meeting in Brussels to discuss the matter and in New York, Turkey asked the U.N. Security Council to take the "necessary action" to stop Syrian aggression.

In a letter to the president of the 15-nation Security Council, Turkish U.N. Ambassador Ertugrul Apakan called the firing of the mortar bomb "a breach of international peace and security."

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'Risks to our national security'
Turkey's parliament had already been due to vote on Thursday on extending a five-year-old authorization for foreign military operations, an agreement originally intended to allow strikes on Kurdish militant bases in northern Iraq.

But the memorandum signed by Erdogan and sent to parliament overnight said that despite repeated warnings and diplomatic initiatives, the Syrian military had launched aggressive action against Turkish territory, presenting "additional risks."

"This situation has reached a level of creating a serious threat and risks to our national security. At this point the need has emerged to take the necessary measures to act promptly and swiftly against additional risks and threats," it said.

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"Our armed forces in the border region responded immediately to this abominable attack in line with their rules of engagement; targets were struck through artillery fire against places in Syria identified by radar," Erdogan's office said in a statement late on Wednesday.

"Turkey will never leave unanswered such kinds of provocation by the Syrian regime against our national security."

Syria said it was investigating the source of the mortar bomb and urged restraint. Information Minister Omran Zoabi conveyed his condolences to the Turkish people, saying his country respected the sovereignty of neighboring countries.

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Some residents of Akcakale abandoned their homes close to the border and spent the night on the streets. Others gathered outside the local mayor's office, afraid to return to their homes as the dull thud of distant artillery fire rumbled across the town.

"We haven't been able to sleep in our own homes for 15 days, we had to sleep in our relatives' houses further away from the border because it's not safe down there," said shopkeeper Hadi Celik, 42, a father of five.

Washington sees Turkey as a pivotal player in backing Syria's opposition and planning for the post-Assad era. The White House said on Wednesday it stood by "our Turkish ally." But Ankara has found itself increasingly isolated and frustrated by a lack of international consensus on how to end the conflict.

Murad Sezer / Reuters

Turkish soldiers patrol near the Akcakale border gate on Thursday.

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Erdogan long cultivated good relations with Assad, but became a harsh critic after Syria's popular revolt began last year, accusing him of creating a "terrorist state." Erdogan has allowed Syrian rebels to organize on Turkish soil and pushed for a foreign-protected safe zone inside Syria.

Reuters and The Associated Press contributed to this report.

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