Heavy smoke billows following an airstrike on the western frontline of Raqa on July 17, 2017, during an offensive by the US-backed Syrian Democratic Forces, a majority Kurdish and Arab alliance, to retake the city from Islamic State (IS) group fighters. (AFP Photo)

DAMASCUS, July 24 (Xinhua) -- At least 30 civilians were killed on Monday when a U.S.-led airstrike hit a prison run by the Islamic State (IS) in Syria's northern city of Raqqa, local Sham FM radio reported.

The strike by the U.S.-led coalition struck the prison, where the civilians were held captives by IS in the central part of Raqqa, said the report.

The attack came hours after the U.S. coalition struck areas in Mayadeen city in the eastern province of Deir al-Zour, killing tens of people, according to the state TV.

Since entering Syria to fight IS in 2014, the U.S. coalition has killed tens of civilians in areas controlled by IS in northern and eastern Syria.

The U.S. has been recently heavily backing the Kurdish-led Syrian Democratic Forces in their push to capture Raqqa, the de facto capital of IS in Syria.