The Turkish air force carried out its first strikes in Syria in 17 months on Saturday, against a northern zone held by Kurdish militia, a war monitor said.
"A Turkish fighter jet struck military positions of Syrian Democratic Forces in Saida village in Ain Issa countryside ... which caused loud explosions," the Syrian Observatory for Human Rights said.
It was the first aerial raid since Operation Peace Spring, it said, an October 2019 military campaign launched by Ankara and its Syrian allies against the SDF in northern Syria.
That operation, interrupted after two accords negotiated by Ankara, the first with Washington, and the second with Moscow, allowed Turkey to seize control of a "safe zone" in Syria about 120 kilometres long and 32 kilometres deep.
But the village of Ain Issa stayed in the hands of Kurdish forces.
Also on Saturday, “violent clashes” and “intensive rocket fire” between the SDF and Turkish-backed factions were reported on the front lines of Ain Issa district, the Observatory reported.
It said casualties had been confirmed.
"Clashes between the two sides have been going on for the past 24 hours ... Turkish forces have had difficulty advancing since the SDF destroyed a Turkish tank," the Observatory director, Rami Abdul Rahman, said.
The Syrian-Kurdish-led People’s Protection Units, which form a vital component of the SDF, are considered by Turkey to be a “terrorist offshoot” of the outlawed Kurdistan Workers’ Party.
But they were also a key ally to the US and others in the battle against ISIS in Syria.