More than 235,000 flee northwest Syria flare-up: UN

The mass displacement between 12 and 25 December has left the violence-plagued Maaret al-Numan region in southern Idlib "almost empty", the UN said in a statement.

Since mid-December, Russian-backed regime forces have pressed with an assault on jihadists in southern Idlib, despite an August ceasefire deal and calls for a de-escalation from Turkey, France and the United Nations.

The increased air strikes came as Russian-backed regime forces advance on the ground.

They have since December 19 seized dozens of towns and villages from the jihadist amid clashes that have killed hundreds on both sides.

The bombardment and clashes have amplified displacement from Maaret al-Numan and the nearby town Saraqeb in the southern Idlib region, the UN said.

"People from Saraqab and its eastern countryside are now fleeing in anticipation of fighting directly affecting their communities next," a statement said.

Idlib is dominated by the country's former Al-Qaeda affiliate, Hayat Tahrir al-Sham, whose chief this week urged jihadists and allied rebels to head to the frontlines and battle "the Russian occupiers" and the regime.

The region hosts some three million people, including many displaced by years of violence in other parts of Syria.

The Damascus regime, which now controls 70 per cent of Syria, has repeatedly vowed to take back the area.

Backed by Moscow, Damascus launched a blistering offensive against Idlib in April, killing around 1,000 civilians and displacing more than 400,000 people.

Despite a ceasefire announced in August, the bombardment has continued, prompting Turkey this week to press for a fresh ceasefire deal during talks in Moscow.

France on Tuesday called for an "an immediate de-escalation", warning of deteriorating humanitarian conditions.

The war in Syria has killed more than 370,000 people and displaced millions since it began with anti-government demonstrations brutally crushed by security forces.