US-led coalition airstrikes on Thursday evening killed at least 35 civilians in an eastern Syrian town held by the Islamic State group, the Syrian Observatory for Human Rights said. The airstrikes targeted areas under the control of Islamic State group in Mayadeen, a town in Syria’s oil-rich eastern province of Deir Ezzor.

Obersvatory head Rami Abdel Rahman said at least 26 among the dead were relatives of the militant group’s fighters, many of them women and children from Syria and Morocco. “The other nine are Syrian civilians and include five children,” Abdel Rahman told AFP.

After 15 people were killed in US-led strikes on the town on Wednesday, the known deaths from two days of coalition bombing raids on Mayadeen reached 50 on Thursday, the Observatory said. Coalition strikes have killed a total of 225 civilians in Syria between April 23 and May 23 of this year, the organisation added.

A Pentagon investigation concluded on Wednesday that at least 105 civilians had died in an anti-jihadist air strike on an Islamic State weapons cache in Mosul in March.