A Russian-backed regime onslaught in northern Syria was reported today to have killed more than 500 people this month, as Turkey faced new pressure to open its border to people fleeing the violence.
World powers urged Russia to end its air strikes which a senior US official said were "directly enabling" the Islamic State group, and the UN Security Council met to discuss the conflict.
The meeting behind closed doors came ahead of crucial international talks tomorrow in Munich to push for Syrian peace negotiations.
The Syrian Observatory for Human Rights said 506 people had died since the regime launched a major offensive against rebels in Aleppo province on February 1.
They include 23 children who were killed in Russian air strikes, according to the Britain-based monitor, which relies on a network of sources on the ground.
Tens of thousands of Syrians were still stranded today at the Oncupinar border crossing, which remained closed.
Turkey is already hosting 2.7 million Syrian refugees and has refused to let a new wave into the country, instead providing humanitarian assistance over the border in Syria.
Many are sleeping in tents or the open, with emergency camps already full.
Medical aid group Doctors Without Borders (MSF) said Wednesday the healthcare system around the war-torn town of Azaz in Aleppo province was "close to collapse" due to the fighting.
Since Saturday, an MSF hospital near Azaz has seen an increase of about 50 per cent in its outpatient department. Many are suffering respiratory tract infections.
"Azaz district has seen some of the heaviest tolls of this brutal war, and yet again we are seeing healthcare under siege," said Muskilda Zancada, the head of MSF's Syria mission.
Those who have fled the offensive tell of scenes of terror and suffering.
"Children are dying under bombs and from hunger and cold. They are living on the roads. They don't have any place to stay," said Abdul Karim Bahloul, who crossed into Turkey this morning.
Human rights groups weighed in, urging Turkey to accept those stranded on its border.
"Forcing people to remain in a war zone, where they risk death and injury, is no solution to the challenge of protecting Syrians fleeing their country," said Human Rights Watch.
