DAMASCUS: Rebel rocket fire killed four children and a woman Sunday in a regime-held town outside the embattled jihadist bastion of Idlib in northwest Syria, state news agency SANA said.

The bombardment by "terrorist groups" on the Christian-majority town of Suqaylabiyah in Hama province also wounded six other children, SANA said, using its term for rebels and jihadists.

The Syrian Observatory for Human Rights said the rockets had been fired from the nearby Idlib region, which is controlled by former Al-Qaeda affiliate Hayat Tahrir al-Sham.

The Britain-based war monitor said it was unclear whether HTS or other insurgent groups were behind the attack.

That region of some three million people is supposed to be protected from a massive regime assault by a September buffer zone deal signed by government ally Russia and rebel backer Turkey.

But Damascus and its allies have upped their deadly bombardment of the edges of the jihadist bastion in recent weeks, killing dozens and causing tens of thousands to flee, according to the Observatory.

They have also taken several towns this week from the jihadists near Suqaylabiyah.

UN-linked aid groups have suspended activities in parts of the Idlib region, as the increased violence since late April has jeopardised the safety of humanitarian workers.

The uptick in air strikes and shelling also displaced 180,000 people between 29 April and 9 May, according to the UN.

The civil war in Syria has killed more than 370,000 people and displaced millions since it started with the brutal repression of anti-government protests in 2011.