ISTANBUL (Reuters) – One Turkish soldier was killed and two were wounded in the northwestern Syrian region of Idlib on Friday in an attack on an armoured ambulance, Turkey’s Defence Ministry said.

Turkish forces identified targets in the area and immediately opened fire in retaliation, the ministry statement said. It did not say who carried out the attack and did not specify where it occurred.

Turkey and Russia back opposing sides in Syria’s war, with Ankara backing rebels fighting against President Bashar al-Assad. Moscow supports Damascus.

Ankara and Moscow agreed on a ceasefire in Idlib on March 5 following weeks of clashes between the warring parties that brought the two countries close to direct confrontation.

Fighting in Idlib escalated in December and displaced nearly a million people, raising concerns of a fresh wave of migrants towards Turkey, which already hosts nearly 4 million refugees.

Turkish President Tayyip Erdogan has accused Assad’s forces of violating the ceasefire, warning they would suffer “heavy losses” if they persisted.

The ministry reported on May 27 that a Turkish soldier was killed in Idlib after an explosion on a key highway which runs through the region.