More than 630 civilians were killed in the six-month operation against the Islamic State group that culminated in its defeat by US-backed Syrian forces on Saturday, a monitor said.
The civilian dead -- among them relatives of IS fighters -- included 209 children and 157 women, the Syrian Observatory for Human Rights monitoring group said.
The Kurdish-led Syrian Democratic Forces launched their offensive against the jihadists' last bastions in the Euphrates Valley on September 10, taking town after town before finally announcing victory in the village of Baghouz on Saturday.
The Britain-based Observatory said the operation had cost the lives of 730 SDF fighters while 1,600 jihadists were also killed.
The SDF does not usually divulge its losses for months.
The Observatory says its figures are drawn from a network of sources inside Syria.