Syrian activists say at least 40 people were killed by air raids on two villages in eastern Syria on January 22.
The Syrian Observatory for Human Rights said the air raids killed some 30 people in the village of Tabiah and another 10 people died in a separate raid on the village of Bouleil.
According to the Britain-based monitoring group, the two villages have been targeted since January 16 by Syrian and Russian air strikes but the claim cannot be independently confirmed.
Opposition activist Omar Abu Leila said all of the victims on the January 22 raids were civilians.
The Observatory said more than 90 people, including whole families, have been killed in Tabiah and Bouleil since the raids began on January 16.
Tabiah and Bouleil -- located in the province of Deir al-Zur -- are both held by the Islamic State extremist group, which also controls most of the province.