MOSCOW (AP) — The Russian military said three of its troops were wounded Tuesday in an attack by militants in northwestern Syria.

Rear Adm. Vyacheslav Sytnik, the chief of the Russian military's Reconciliation Center in Syria, said that militants in the province of Idlib fired an anti-tank missile at a Russian armored personnel carrier, wounding three military police officers.

He said the attack happened while the Russian troops were on patrol near Trumba in Idlib and Turkish troops were pulling out of the area.

Russia and Turkey, which have backed opposing sides in the Syrian conflict, negotiated a cease-fire deal for Idlib that envisaged joint patrols and established observation posts to monitor the truce, which has been frequently violated.

Russia is the Syrian government’s main military ally, while Turkey has backed the Syrian opposition.

Russia has waged a military operation in Syria since 2015, tipping the balance of power in favor of President Bashar Assad and helping his government reclaim control over most of the country after a devastating civil war.