ANKARA: A suspected Syrian army helicopter dropped barrel bombs on Turkish-backed rebels Tuesday, the Turkish military said, in what appeared to be the first direct clash with Syrian forces since Turkey launched a cross-border incursion in August.

A helicopter "assessed to belong to regime forces" bombed the rebels in a village near Akhtarin, a town 5 km (3 miles) southeast of Dabiq, the Turkish military said in a statement. Dabiq is a former ISIS stronghold which the rebels seized from the extremists this month.

Two Turkish-backed rebels were killed and five wounded, the statement said. The Syrian military could not immediately be reached for comment.

The Syrian military said last week the presence of Turkish troops on Syrian soil was a "dangerous escalation and flagrant breach of Syria's sovereignty". It warned it would bring down any Turkish warplanes entering Syrian air space.

Turkey launched "Operation Euphrates Shield" two months ago, sending tanks and warplanes into Syria in support of the largely Turkmen and Arab rebels to push ISIS from the border and prevent Kurdish militias taking ground in their wake.

President Tayyip Erdogan said Saturday the Turkish-backed forces would press on to the ISIS-held town of al-Bab, around 15 km (9 miles) from their current position. The Kurdish YPG militia is also seeking control of the town.