Turkey began a new air and ground operation to oust Kurdish militia from their northern Syrian enclave, defying US warnings that this could further destabilise the area after almost seven years of civil war.

A spokesman for Britain's Foreign Office said they were "closely following developments" in the Afrin area.

"The UK has regularly discussed issues relating to the conflict in Syria with the Turkish authorities, in line with our shared aim of reducing violence and enabling a political settlement," the spokesman told AFP.

"We recognise that Turkey has a legitimate interest in the security of its borders.

"The UK is committed to working closely with Turkey and other allies to find solutions in Syria that provide stability, refrain from escalating the situation and protect Turkey's security interests."

Turkish President Recep Tayyip Erdogan had repeatedly vowed that Turkey would root out the "nests of terror" in Syria of the People's Protection Units (YPG) militia which Turkey deems a terror organisation.

The launch came despite warnings that the operation could be militarily tough against an already battle-hardened foe and complicate relations with both Washington and Moscow.