The more than four-month-long battle for Raqa, which US-backed forces declared over Tuesday, has left at least 3,250 people dead, more than a third of them civilians, a monitor said.

The Syrian Observatory for Human Rights said that at least 1,130 civilians were among those killed since the start of the operation in early June. Hundreds more were still missing and may have been buried alive in their homes by shelling, bombs and air strikes.