Turkish tanks and attack aircraft have clashed with Kurdish-led forces in northern Syria, just hours after hopes were raised about a new general ceasefire in the war-torn country.
Fighters aligned with the Syrian Democratic Forces, a Kurdish-led alliance that is supported by the United States, engaged Turkish forces, including tanks and Ankara-backed Syrian rebels, south of the border town of Jarablus.
Nour el-din el-Zinki, an Ankara-backed rebel group, claimed it captured a village and took two Kurdish prisoners during the clashes.
Earlier Turkish jets bombed an ammunition dump and command centre for "terror groups", Ankara said, on the fourth day of an intervention designed to clear Isis (Islamic State) from border areas and contain Kurdish expansion.
The Jarablus Military Council group, which is allied to the SDF, said a Turkish air strike in the village of al-Amarna caused civilian casualties and called it "a dangerous escalation that threatens the fate of the region".
Turkish forces and allied Syrian rebels entered Syria and seized Jarablus from Isis in an operation dubbed "Euphrates Shield."
Turkey appears to have rapidly expanded its forces there since, with local media reporting 50 tanks and 380 personnel inside Syria after three days of operations.
Recep Tayyip Erdogan, the Turkish President, has made it clear that the offensive is also aimed at reversing recent Kurdish territorial gains and has demanded the SDF withdraw east of the Euphrates River.
SDF units crossed the Euphrates in a US-backed operation to liberate the Isis stronghold of Manbij last month.
The Turkish intervention appears to have been prompted in part by fears the SDF might also liberate Jarablus.
The SDF, which is spearheaded by the YPG, a Syrian Kurdish militia, has been lauded by both Russia and the West as one of the most effective forces fighting Isis, and has received extensive US support.
Turkey considers the YPG a branch of the Kurdistan Workers Party, a group that has fought a three decade insurgency against the Turkish state, and is determined to prevent the group establishing an autonomous region in northern Syria.
The US has struggled to balance its alliance with Syrian Kurds and Turkey, a key Nato ally.