Turkey's state-run news agency says a helicopter believed to belong to Syrian government forces has dropped barrel bombs in a deadly attack on Turkey-backed opposition forces in the border area.

The Anadolu Agency, quoting military officials, reported on Wednesday that two opposition fighters were killed in the attack in the village of Tall Nayif in northern Syria while five others were wounded. The agency didn't say when the attack happened.

Turkey sent troops and tanks into Syria in August to support Syrian opposition forces efforts to clear the border area of Islamic State fighters.

Ankara is also seeking to contain the U.S.-backed Syrian Kurdish forces fighting IS. Turkey says the Kurdish forces are linked to Turkey's outlawed Kurdish insurgents and the Turkish government considers both to be terrorist groups.