Ankara: Turkey launched a ground offensive against Kurdish separatist fighters and Islamic State positions in northwest Syria on Sunday after President Recep Tayyip Erdogan ignored calls from the US to avoid attacking Afrin.

Turkish tanks crossed into the Syrian town of Azaz and were advancing toward the Kurdish stronghold of Afrin, the Hurriyet newspaper said. The incursion came after Turkish F-16s and artillery units hit almost all targets in the operation against Kurdish YPG and Islamic State positions, Prime Minister Binali Yildirim said on television late Saturday.

The army said 72 warplanes took part using Syrian airspace. Turkish General Hulusi Akar said troops suffered some casualties in the operation, which also included Turkish-backed Syrian rebels from the Free Syrian Army.

Turkey is using self-defence under international law, and the "Olive Branch" operation is aimed at eliminating Kurdish PYD/YPG forces along with the Islamic State, the army said, accusing the YPG of using civilians as human shields. Turkey has been outraged by plans to create a border security force using thousands of Kurdish fighters by the American-led coalition against the Islamic State, saying the Kurdish fighters have designs on Turkish territory.