Jihadist-run Idlib has come under mounting bombardment in recent weeks, forcing tens of thousands to flee their homes in the region of some three million people.

"Regime air raids killed five civilians in the town of Ariha," said the Syrian Observatory for Human Rights, which relies on sources inside the war-torn country.

The Damascus government has repeatedly vowed to take back control of Idlib, which is run by Hayat Tahrir al-Sham, a group dominated by Syria's former Al-Qaeda affiliate.

A ceasefire announced in late August was supposed to stem Russia-backed regime bombardment of the region after it killed around 1,000 civilians in four months.

But the Observatory says sporadic bombardment and clashes continued, before intensifying in the past month.

On January 1, missiles fired by regime forces killed nine civilians including five children in a school turned shelter in the town of Sarmeen.

Syria's war has killed more than 380,000 people including over 115,000 civilians since it started in 2011 with the brutal repression of anti-government protests.

In total 11,215 people including more than 1,000 children were killed last year, although it was the least deadly year on record since the beginning of the conflict.