Turkish jets have bombed the city of Afrin in northern Syria, as President Recep Tayyip Erdogan promised to expand Turkey’s military border operations against a Kurdish group allied to the US in the fight against Islamic State.

The warplanes attacked Afrin, which is controlled by the Kurdish People’s Protection Units (YPG), shortly before sunset, Turkish media reported.

A Kurdish official confirmed the strikes, saying they were the first by the Turkish military on the city in what it has named operation Olive Branch.

The attack follows a week of threats by the Turkish government to clear the YPG from Afrin and its surrounding countryside.

Turkey said the YPG — a group it considers a terrorist organisation — is an extension of an outlawed Kurdish rebel group fighting inside its own borders. It has recruited to its cause thousands of disaffected Syrian opposition fighters, who view the YPG as a counter-revolutionary force in Syria’s multi-sided civil war.

Associated Press journalists at the Turkish border saw a convoy of buses, believed to be carrying Turkish-backed Syrian opposition fighters, travelling along the border across from Afrin.

A convoy of buses believed to be carrying Syrian opposition fighters, travels along the border with Syria (AP)
A convoy of buses believed to be carrying Syrian opposition fighters, travels along the border (AP)

The convoy included at least four trucks carrying pickup trucks mounted with machine guns. Video from Turkey this week showed the military moving tanks to the border.

The YPG is the driving force behind a coalition of north Syrian forces allied with the US to battle IS. With American support, including close to 2,000 embedded forces, the coalition now controls close to a quarter of Syrian territory, concentrated mostly in the north-east.

Turkish leaders were infuriated by an announcement by the US military one week ago that it was going to create a 30,000-strong border force with the Kurdish fighters to secure northern Syria.

Days later, US secretary of state Rex Tillerson announced that the US would maintain a military presence with the Kurds for the foreseeable future.

Military aircraft flies over Syria during 'Operation olive branch' (AP)
Military aircraft flies over Syria during ‘Operation olive branch’ (AP)

Speaking in the city of Kutahya in western Turkey, Mr Erdogan announced an expansion to Turkish operations in Syria, promising to move on the Kurdish-controlled town of Manbij and its surrounding countryside after completing operations in Afrin, to force out the Kurdish militia from all positions west of the Euphrates river.

Turkish prime minister Binali Yildirim said the strikes on Afrin marked the start of a campaign to “eliminate the PYD and PKK and Daesh elements in Afrin”, in reference to the Kurdish Democratic Union Party and the Kurdistan Worker’s Party respectively, and using an Arabic acronym for IS.

The PYD, PKK, and YPG all look to the Kurdish Marxist-nationalist leader Abdullah Ocalan as their guide. Ocalan has been imprisoned by Turkey for waging a separatist movement in the eastern part of the country.

The air strikes were preceded by an artillery bombardment on the Afrin region.

Any ground operation would entail considerable military and political risk for Ankara. Russia keeps military observers in Afrin and has lately firmed up its ties with the YPG. Meanwhile, Syria’s government in Damascus has said it will shoot down any Turkish jets on raids in the country.