The United Nations aid chief called Tuesday for an end to bombings in Syria's Aleppo province after air strikes sent tens of thousands of civilians fleeing toward the Turkish border.

"The highest need and the best humanitarian response is for the bombing to stop," Stephen O'Brien said, when asked if Russia should halt its air campaign in the area.

"All bombings should stop."

Syrian government forces backed by Russian air power have captured a string of villages around opposition-held Aleppo over the past week and managed to cut a major rebel supply route to the city.

Up to 35,000 people have fled the area in recent days, O'Brien said, adding that many have been forced to turn back toward Idlib after finding the border closed.

The United Nations is also urging Turkey to open its borders to allow fleeing Syrians to cross into safe territory and to send aid supplies to the displaced.

"A lot of people (are) currently on the move and to some degree back and forth on that route," said O'Brien, the under-secretary-general for humanitarian affairs and emergency relief.

The Russian-backed offensive on Aleppo has continued as the United Nations pressed ahead with preparations for a new round of peace talks on February 24.

Russian Foreign Minister Sergei Lavrov is to join US Secretary of State John Kerry in Munich on Thursday for a meeting of the 17-nation Syria support group that was set up to shepherd the peace talks.

UN spokesman Stephane Dujarric said the Munich meeting will be "critical to ensure that all those around the table have a positive influence" on the warring sides to reduce the violence.

Syria's nearly five-year-old war has killed 260,000 people and displaced half the population.

Syria air strike hits MSF-supported hospital, 3 dead: statement
Paris (AFP) Feb 9, 2016 - An air strike hit a hospital in southern Syria that is supported by Doctors Without Borders (MSF), killing three people and wounding six, the medical charity said on Tuesday.

"The strike on Tafas field hospital, some 12 kilometres (seven miles) from the Jordanian border, took place on the night of February 5. It caused partial damage to the hospital building, and put its heavily-used ambulance service out of action," MSF said in a statement.

A nurse was among the casualties, it added.

"The hospital is the latest medical facility to be hit in a series of air strikes in southern Syria, which have been escalating over the past two months," it said, without specifying who was behind the strikes.

In addition to the Syrian government, Russia and a US-led coalition targeting the Islamic State group are also carrying out raids in the war-torn country.

A Syrian aid group in January said 177 hospitals had been destroyed and nearly 700 health workers killed since the outbreak of the country's civil war in March 2011.

It is not the first time MSF-supported facilities in Syria have been hit.

"Since the start of this year alone, 13 health facilities in Syria have been hit, confirming that hospitals and clinics are no longer places where patients can recover in safety," the charity said.

"This latest incident further depletes Syria's already exhausted healthcare system, and prevents more people from accessing desperately needed medical care," it added.