Around 350,000 Syrians, mostly women and children, have fled a renewed Russian-backed offensive in the opposition-held Idlib province since early December, and have sought shelter in border areas near Turkey, the United Nations said on Thursday, Reuters reports.
The humanitarian situation continued to deteriorate as a result of the "escalating" hostilities, the UN Office for the Coordination of Humanitarian Affairs (OCHA) said in its latest situation report.
Russian jets and Syrian artillery have pounded towns and villages in recent weeks in a renewed assault backed by pro-Iranian militias and aimed at clearing the opposition.
"This latest wave of displacement compounds an already dire humanitarian situation on the ground in Idlib," David Swanson, Amman-based UN regional spokesman for Syria, told Reuters.
Russian and Syrian jets resumed bombing of civilian areas in the opposition enclave two days after a ceasefire agreed between Turkey and Russia formally took effect on Sunday.
Karen AbuZayd, a UN war crimes investigator on Syria, told reporters in Geneva that many of the destroyed or closed schools in opposition-held areas were now being used as shelters for people fleeing the violence.
The latest wave of displaced people comes on top of close to 400,000 people who fled earlier fighting for the safety of camps near the Turkish border, UN officials say.
Paulo Pinheiro, chairman of the UN Commission of Inquiry on Syria, told reporters on Thursday that many uprooted families now in makeshift camps were running short of food and water.
The latest offensive has brought the Russian-steered military campaign closer to heavily populated parts of Idlib province, where nearly 3 million people are trapped, according to the United Nations.
Rescuers and residents said that on Thursday Russian and Syrian jets pounded the devastated city of Maarat al-Numan. It is one of the main urban centres in the province and lies on a main highway held by rebels.
The army and Iranian-backed militias are advancing towards the city. Its capture would be a strategic gain in the current campaign whose goal is also to regain control of major trade arteries important to Syria's war-torn economy.
On Wednesday at least 21 civilians were killed in heavy aerial strikes, among them 19 people who died when bombs were dropped on a busy market place in the centre of Idlib city, the provincial capital.