At least 29 people, including a woman, were killed, in an airstrike in a rebel-held area in Syria's Deir al-Zour province, a monitor group reported.
Several people were also wounded, some critically, when unknown warplanes struck the town of Khusham on Saturday in the eastern countryside of Deir al-Zour, Xinhua news agency reported quoting the Syrian Observatory for Human Rights.
It added that it was not clear whether the strikes were carried out by Syrians or Russians.
The Britain-based watchdog group said the attack on Khusham came just a day after 44 people, including 15 children and eight women, were killed in similar airstrikes against areas in eastern Deir al-Zour.