"Eleven fighters were killed in a Turkish air strike that hit a Syrian regime outpost... near the Turkish border," the Syrian Observatory for Human Rights said, without specifying if the victims were affiliated with the Damascus government or Kurdish forces.

The Kurdish-led Syrian Democratic Forces said "Turkish military aircraft have conducted 12 airstrikes against positions of the Syrian army deployed on the border strip west of Kobane," a Kurdish-held town.

The raids caused "casualties", SDF spokesman Farhad Shami said, without specifying how many.

Syrian regime forces have deployed in areas controlled by Kurdish fighters near the border with Turkey as part of agreements intended to stem cross-border offensives by Ankara targeting Kurdish forces it views as terrorists.

Tuesday's raids followed overnight clashes between Ankara's forces and the Kurdish-led SDF west of Kobane, said the Observatory, a Britain-based monitoring group that relies on a network of sources inside Syria.

As part of the escalation, Kurdish forces struck inside Turkish territory, killing one soldier, according to Turkey's defence ministry.

"Thirteen terrorists were neutralised" in retaliatory attacks by Ankara inside Syria, the ministry said, adding operations were ongoing in the region.

Turkey has launched a series of cross-border offensives targeting Kurdish forces and the Islamic State group since 2016, but such operations have rarely resulted in the killing of Syrian regime fighters.

If regime forces are confirmed to be among those killed on Tuesday, the attack would mark one of the largest escalations since Ankara and Damascus traded attacks in 2020 following a Syrian regime strike that killed 33 Turkish soldiers in the northwestern province of Idlib.

Turkey has stepped up its attacks in Kurdish-controlled areas of Syria since a July 19 summit with Iran and Russia failed to green-light a fresh offensive.

The SDF, the Syrian Kurds' de facto army, has since counted at least 13 of its members killed in several Turkish attacks.

Turkey has fervently opposed Syrian President Bashar al-Assad, backing rebels calling for his removal and opening its doors to refugees.

But last week, Turkish Foreign Minister Mevlut Cavusoglu called for reconciliation between the Syrian government and the opposition.

Cavusoglu's comments had been seen as an apparent easing of Ankara's long-standing hostility towards Assad's government and enraged the Syrian opposition and rebel groups.