Turkish jets have begun an aerial offensive against the Syrian Kurdish-held enclave of Afrin in north-western Syria, Turkish Prime Minister Binali Yildirim said.

“As of this moment our brave Armed Forces have started the aerial offensive to eliminate the PYD and PKK and Daesh elements in Afrin,” he said at a speech in the city of Bilecik, referring to the Kurdish Democratic Union Party and the Kurdistan Worker’s Party respectively, and using an Arabic acronym for the Islamic State group.

Turkey’s state-run news agency, meanwhile, said that a group of Turkish-backed Syrian opposition forces crossed into the area on Saturday as part of an offensive to oust a militia group Turkey considers to be terrorists.

Theresa May meets Turkish PMBinali Yildirim said Turkish jets have begun an aerial offensive against Afrin (Matt Dunham/PA)

Associated Press journalists at the Turkish border saw at least five jets heading towards Afrin.

They also witnessed a convoy of buses, believed to be carrying Syrian opposition fighters, travelling along the border across from Afrin.

The convoy included trucks mounted with machine guns.

Rojhat Roj, a spokesman for the Syrian Kurdish militia group, confirmed that a Turkish plane was striking Afrin city.