Eleven pro-Turkish Syrian fighters were killed Thursday by Kurdish forces in violation of ceasefire agreements aimed at creating a "safe zone" in northern Syria, Turkey's President Recep Tayyip Erdogan said.
"This morning, 11 members of the Syrian National Army were martyred," Erdogan told a press conference in Ankara, using the name for a Syrian militia fighting for Turkey.
"Of course, a bigger number died on the other side... When they attack the SNA or our soldiers, should we stay silent? Of course, we have to retaliate -- more than retaliate," he added.
Erdogan did not say where the fighting had taken place, but the Syrian Observatory for Human Rights, a monitor, said clashes had taken place near the Syrian border town of Ain Issa, without detailing casualties.
Turkey launched an offensive in northern Syria last month aimed at establishing a "safe zone" that would push Kurdish forces away from its border and create room to repatriate Syrian refugees.
It halted the offensive after two ceasefire accords -- with Washington and Moscow -- that called on the Kurdish People's Protection Units (YPG) to abandon most of its positions in a 30-kilometre-deep stretch of territory along the Turkish border.
Erdogan again criticised the failure of the United States and Russia to ensure the full withdrawal of the YPG from the agreed areas.
"Those who promised us the YPG would withdraw within 120 hours have not fulfilled this at this stage," he said.
"Similarly with Russia... unfortunately 150 hours have passed but so far all the terrorists have not left from these areas."
Erdogan is due to discuss the situation with his counterpart Donald Trump during a visit to Washington on November 13, and said he would also speak with Russian President Vladimir Putin by phone.