Artillery fire early Friday morning on the village of Kansafra in the northwestern stronghold killed four children from the same family, the Britain-based Syrian Observatory for Human Rights said.

An AFP correspondent saw the father cry over the bodies of three of the children at a cemetery. The remains of a fourth were then brought along, and buried in haste as shelling started up again in a neighbouring area.

A day earlier, in the nearby village of Balshun, artillery fire by pro-Damascus forces killed four children and the mother of three of them, the Observatory reported.

The Idlib region is home to nearly three million people, two-thirds of them displaced from other parts of the country during the decade-long civil war.

It is dominated by Syria's former Al-Qaeda affiliate, but rebels and other jihadists are also present.

A ceasefire deal brokered by regime ally Russia and rebel backer Turkey has largely protected the region from a new government military offensive since March 2020.

But regime forces have stepped up their shelling on the southern edges of the bastion since June.

Syrian President Bashar al-Assad took the oath of office for a new term last month, vowing to make "liberating those parts of the homeland that still need to be" one of his top priorities.

Syria's war has killed around half a million people since starting in 2011 with a brutal crackdown on anti-government protests.