DAMASCUS, Sept. 23 (Xinhua) -- The U.S.-led coalition air strikes against the Islamic State group in Syria has killed thousands of civilians since they entered the course of Syrian war four years ago, a war monitor reported on Sunday.

The Syrian Observatory for Human Rights said the death toll of civilians is part of a total of 12,000 rebels and ultra-radical militants killed by the U.S.-led strikes.

The UK-based watchdog group said the overall death toll also includes 169 soldiers with the Syrian army and allied forces. They were killed by the U.S.-led attacks on Syrian military positions.

The U.S.-led coalition has been recently backing the Kurdish-led Syrian Democratic Forces (SDF) in their push to defeat IS in the last remaining pocket in the eastern countryside of the oil-rich province of Deir al-Zour.

The Syrian government, citing the death toll of civilians throughout the last four years, has repeatedly urged the UN to push for the withdrawal of the coalition from Syria.