The UN Security Council has strongly condemned a mortar attack by Syria on a Turkish border town that killed five people.

The Security Council demanded that "such violations of international law stop immediately and are not repeated."

"The members of the Security Council underscored that this incident highlighted the grave impact the crisis in Syria has on the security of its neighbours and on regional peace and stability," the 15-member council said in a statement.

The council "called on the Syrian government to fully respect the sovereignty and territorial integrity of its neighbours."

The mortar attack happened yesterday, and Turkey responded by striking targets in Syria both yesterday and today.

Earlier, Syria apologised through the UN for the mortar strike and said such an incident would not be repeated.

"Syria accepts that it did it and apologises. They said nothing like this will happen again. That is good. The UN mediated and spoke to Syria in the evening," Turkish Deputy PM Besir Atalay said.

Turkey's parliament gave authorisation earlier today for military operations outside Turkish borders.

The government had sought parliamentary approval to send soldiers to foreign countries in a memorandum which said that "aggressive action" by Syria's armed forces against Turkish territory posed a serious threat to national security.

Turkey's military said soldiers loyal to Syrian President Bashar al-Assad had been killed by the Turkish artillery fire.

Ibrahim Kalin, a senior adviser to Prime Minister Tayyip Erdogan, said on his Twitter account that Turkey had no interest in a war with Syria but would protect its borders.

He said political and diplomatic initiatives would continue.

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