Air strikes by regime and Russian aircraft on rebel positions in the northwestern province of Idlib killed at least 21 civilians, including eight children, a monitor said Monday.

The strikes carried out on Sunday were the latest against jihadists and rebels in a week-old regime offensive on Idlib, the last province in Syria to escape government control.

The raid left "at least 21 dead, including eight children and 11 members of the same family" west of the town of Sinjar in the southeast of the province, the Syrian Observatory for Human Rights said.

"Regime and Russian strikes are continuing today on several parts of Idlib" province, Rami Abdel Rahman, the head of the Britain-based monitoring organisation, told AFP.