An intensified bombardment by Russian forces and the Syrian regime has pushed thousands of people to flee to the border with Turkey, residents and rescue workers are saying.
Clashes between the Syrian regime and armed groups in the country's last major opposition bastion have killed more than 80 on both sides in the past 24 hours, despite UN calls for de-escalation, a war monitor said on Friday.
The Britain-based Syrian Observatory for Human Rights said 42 militants and nine rebels had been killed in battles with regime forces in the northwestern province of Idlib since Thursday night.
The fighting near the rebel-held town of Maarat al Numan also killed 30 Syrian regime loyalists, the Observatory said.
Warplanes from regime ally Russia pounded areas around Maaret al Numan and the nearby town of Saraqeb with a series of air strikes, said the Observatory which relies on a network of sources across Syria.
The flare-up triggered a wave of displacement from nearby areas, said an AFP correspondent in Maarat al Numan.
Thousands of people have fled to the Turkish border from northwestern Syria because of the intensified bombardment, residents and rescue workers told Reuters.
A long line of vehicles was seen on Friday leaving Maarat al Numan which has borne the brunt of the attacks, which included air strikes, they said.
"The exodus is in the thousands. It's a humanitarian catastrophe, we are seeing people walking in the streets and people waiting near the homes for cars to take them out," said Osama Ibrahim, a rescue worker from Maarat al Numan.
Yasser Ibrahim al Dandal said he was fleeing with his family to olive groves in northern Idlib, where they would sleep out in the open.
"Hundreds of rockets hit Maarat al Numan," he told AFP. "The situation is very bad."
Some parts of 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.
Pro-regime 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 the regime of Bashar al Assad has repeatedly vowed to retake the area and the Observatory says deadly bombardment and skirmishes have persisted.
The United Nations this week condemned a deadly rise in violence after the Observatory reported that regime air strikes and artillery fire had killed 23 civilians on Tuesday.
Najat Rochdi, senior humanitarian adviser to the UN's Syria envoy, called for "immediate de-escalation".
Turkish President Recep Tayyip Erdogan, who reached an accord last September with Russia to contain the fighting and whose country is seen by many civilians in opposition areas as a protector, has warned of a renewed refugee influx.
Erdogan said on Thursday 50,000 people were fleeing Syria's northwestern region of Idlib. He did not say whether any of the people fleeing had entered Turkey.
Syria's war has killed over 370,000 people and displaced millions from their homes since it began in 2011 with the brutal repression of anti-government protests.