The UN Security Council has unanimously approved a statement condemning "in the strongest terms" Syria's shelling of a Turkish town that killed five people.

Council members managed to bridge differences between the strong statement demanded by the United States and its Western supporters and backed by their NATO ally Turkey, and a weaker text pushed by Russia, Syria's most important ally, after negotiations that began late on Wednesday and continued until Thursday.

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In the press statement, which needed approval from all 15 council members, the UN's most powerful body said the incident "highlighted the grave impact the crisis in Syria has on the security of its neighbours and on regional peace and stability."

It also extended condolences to the families of the victims and to the government and people of Turkey.

The council demanded an immediate end to such violations of international law and called on the Syrian government ``to fully respect the sovereignty and territorial integrity of its neighbours.'' Russia's agreement that the Syrian shelling violated international law was a key concession by Moscow.

'Terrorists and insurgents'

The original Western-backed draft, proposed by Azerbaijan, condemned the shelling "in the strongest terms" and called it a violation of international law. Proposed Russian amendments never mentioned any breaches of international law, so the inclusion in the final text was a concession by Moscow.

Earlier on Thursday, Syria's UN envoy said his government was not seeking any escalation of violence with Turkey and wanted to maintain good neighbourly relations.

Ambassador Bashar Ja'afari said the government did not apologise for the shelling from Syria because it was waiting for the outcome of an investigation on the source of the firing.

He read reporters a letter he delivered to the Security Council that sent Syria's "deepest condolences" to the families of the victims "and to the friendly and brotherly people of Turkey."

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It urged Turkey and its other neighbours to "act wisely, rationally and responsibly" and to prevent cross-border infiltration of "terrorists and insurgents" and the smuggling of arms.

During Thursday's negotiations on the text when the outcome was still in doubt, US Ambassador Susan Rice told reporters "we think it's very important that the council speak clearly and swiftly to condemn this shelling."

"This sort of cross-border military activity is very destabilising and must be stopped," she said.

The border violence has added a dangerous new dimension to Syria's civil war, dragging Syria's neighbours deeper into a conflict that activists say has already killed 30,000 people since an uprising against President Bashar al-Assad's regime began in March 2011.