A helicopter "assessed to belong to regime forces" dropped barrel bombs on Turkish-backed opposition fighters, the Turkish officials and media reports said on Wednesday.

The attack killed two rebel fighters and wounded five others, the Turkish military said in a statement carried by Turkey's Dogan news agency.

The strike reportedly took place late on Tuesday in a village 5 km (3 miles) southeast of Dabiq. The city is a former "Islamic State" (IS) stronghold which was seized from the Islamist militant group this month by opposition forces.

Turkish Foreign Minister Mevlut Cavusoglu said on Wednesday that Ankara's operations inside Syria will not be deterred. He also accused forces loyal to Syrian President Bashar Assad of not targeting IS militants.

"Their only concern is (to attack) the moderate opposition," he claimed.

If the attack is confirmed, it would be the first direct clash between Syrian government forces and Turkey-backed northern rebels since Turkey sent troops and tanks into Syria in August.

Aleppo advances to be met 'with force'

Syrian government forces also warned Turkey on Wednesday that any advances towards government positions to the north and east of Aleppo would be met "decisively and with force." The comments were made by a Syrian army field commander in a written statement sent to Reuters news agency.

Last week, the Syrian military said the presence of Turkish troops in Syria was "a dangerous escalation and flagrant breach of Syria's sovereignty." The army also warned it would take down any Turkish warplanes entering Syrian airspace.

Turkey sent troops into northern Syria in August in an incursion that Ankara said was an effort to aid Syrian opposition forces in their fight against IS militants. Turkey is also seeking to contain the US-backed Syrian Kurdish forces battling IS, saying those troops are linked to Turkey's outlawed Kurdish insurgents.

rs/kl   (AP, dpa, Reuters)