Air strikes by the Syrian regime and its ally Russia Saturday killed 12 civilians in the country's last major opposition bastion where a rise in violence has forced tens of thousands to flee.

The bombardments hit the northwestern province of Idlib, which has been increasingly targeted this month by President Bashar al-Assad's forces.

The intensification of air strikes on southern Idlib since December 16 has forced tens of thousands to flee their homes, according to the United Nations.

On Saturday, bombing killed eight civilians in the town of Saraqeb, according the Syrian Observatory for Human Rights.

Four others were killed in separate air strikes in other towns in southern Idlib.

And 36 others were wounded, the Britain-based monitoring group added.

The bombardment came as violent clashes continued for a third straight day between regime loyalists and the militants who dominate the province.

Battles since Thursday have killed 67 jihadists and 15 allied rebels, the Observatory said.

Fifty-seven regime loyalists were also killed, bringing the total casualty count to nearly 140 on both sides, it added.

The Idlib region, which is home to some three million people including many displaced by Syria's civil war, is controlled by the country's former Al-Qaeda affiliate, Hayat Tahrir al-Sham.

The Damascus regime has repeatedly vowed to take back control of it.

Pro-government forces launched a blistering offensive against the region in April, killing around 1,000 civilians and displacing more than 400,000 people from their homes.

Since August, the area has supposedly been protected by a ceasefire announced by Moscow, but bombardments have continued.

Copyright Agence France-Presse, 2019