Two Syrian monitoring groups, Deir Ezzor 24 and Justice For Life, said the weapons were dropped on the village of Doblan by an unidentified jet. Russian, Syrian, and US-led coalition aircraft are all known to operate in the area.
Cluster bombs are designed to spread small bomblets across a wide area, but many fail to explode, endangering civilians long after the fighting has ended.
Omar Abou Layla, the head of Deir Ezzor 24, said 15 bodies, including of women and children, were recovered in the village. He said residents expect to find many more killed.
The Britain-based Syrian Observatory for Human Rights put the initial toll at 30 dead.
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At least 57 people were killed in an airstrike on an IS- run jail in the Euphrates River Valley on Monday. Activists said that airstrike was carried out by the US-led coalition. The coalition said it was looking into the reports.
Turkey's military meanwhile said it returned fire after an attack by Syrian Kurdish forces.
A statement today said the People's Protection Units, or YPG, fired on Turkish territory overnight with anti-aircraft weapons from Syria's Afrin region. Turkish artillery units returned fire, destroying the "detected targets."
Turkey was angered by a US decision last month to arm the Syrian Kurds, fearing the weapons will end up in the hands of Kurdish rebels in Turkey.