The raid late Thursday hit a "gathering of civilians" at an ice factory near the village of Al-Soussa near the Iraqi border, the Britain-based Syrian Observatory for Human Rights monitor said.

It was not immediately clear if the strike was carried out by an Iraqi plane or by one of the US-led coalition fighting IS, the monitor said.

Iraqi warplanes have recently carried out strikes in eastern Syria, while coalition aircraft have been supporting Kurdish-led fighters battling the jihadists.

State news agency SANA reported the strike late Thursday, saying more than 30 civilians were killed and accusing the US-led coalition.

The coalition was not immediately available for comment.

IS fighters swept across Syria and Iraq in 2014, declaring a cross-border "caliphate" in areas they controlled.

They have since lost most of that territory to various offensives, but still retain pockets in Syria including in Deir Ezzor.

Al-Soussa lies to the east of the Euphrates River, which runs diagonally through Deir Ezzor, splitting the province in half.

Russia-backed regime forces have pushed back the jihadists on the western side of the Euphrates, while the US-backed Syrian Democratic Forces alliance have battled them to its east.