BEIRUT — The Syrian army has carried out a series of airstrikes against a town in eastern Syria that was captured by fighters from an al-Qaida breakaway group a day earlier, killing 16 people, activists said Saturday.

The Britain-based Syrian Observatory for Human Rights said the warplanes pounded Muhassan and that casualties included three civilians.

Fighters from the Islamic State of Iraq and the Levant stormed Muhassan along the Euphrates River on Friday after rebels from the Western-backed Supreme Military Council defected to the jihadi group, activists said.

The town is in the eastern province of Deir el-Zour, which borders Iraq.