'500 dead' in Syria regime's Aleppo assault

A Russian-backed regime onslaught in northern Syria was reported Wednesday 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 Thursday 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, including 23 children killed in Russian air strikes.

Tens of thousands of Syrians were still stranded Wednesday at the Oncupinar border crossing to Turkey, which remained closed.

Turkish Prime Minister Ahmet Davutoglu on Wednesday said it was building a new camp for the refugees inside Syria, and said it was unfair to ask Turkey to open its borders without pressuring Russia over its bombing.

"I find it hypocritical that some circles are telling Turkey to 'open your borders' while at the same time failing to tell Russia 'enough is enough'," Davutoglu told reporters.

Turkey is already hosting 2.7 million Syrian refugees and has refused to let a new wave into the country, leaving many sleeping in tents or the open.

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 percent in its outpatient department. Many are suffering respiratory tract infections.