Syrian opposition forces on Sunday claimed that Russian jets, in violation of a cease-fire, hit an outpost in northwestern Syria's Idlib province, near the border with Turkey, killing at least one opposition fighter and wounding several others.
They said several overnight raids hit Babeska, a village in Idlib that has become a haven for several moderate Free Syrian Army (FSA) groups.
A tripartite mechanism was established in February by Turkey, Russia and Iran to monitor the ceasefire in Syria.
Opposition forces, however, say Russia has failed to pressure the Assad regime to ensure the ceasefire holds.
The village also houses hundreds of families and fighters from the Damascus suburb of Daraya, which fell to Assad regime forces last year and was evacuated by opposition forces.
Fighter jets, also believed to be Russian, struck the town of Urum al Kubra in the opposition-held western Aleppo countryside where five civilians were killed in an area that has witnessed fighting between the opposition and the Assad regime, the opposition said.