BEIRUT: Air strikes hit a hospital in a rebel-held area of Syria's Aleppo and killed at least 27 people, including three children and the city's last pediatrician, the Syrian Observatory for Human Rights said on Thursday.

A new wave of aerial bombing on Thursday on rebel-held districts of the city killed at least 30 more civilians, a rescue worker said. The Observatory put the toll at least 20.

In government-held areas, rebel mortar shelling killed at least 14 people, the Britain-based Observatory and Syria's state news agency SANA reported.

Escalating violence in Aleppo is pushing people living there to the brink of a humanitarian disaster, the International Committee of the Red Cross (ICRC) said in Geneva.

"Wherever you are, you hear explosions of mortars, shelling and planes flying over," Valter Gros, who heads the ICRC office there, was quoted as saying in the statement.

"There is no neighborhood of the city that hasn’t been hit. People are living on the edge. Everyone here fears for their lives and nobody knows what is coming next," he said.

Aleppo has been the epicenter of a military escalation that has helped to undermine U.N.-led peace talks in recent weeks. A cessation of hostilities agreement has unraveled and fighting has resumed on numerous fronts in western Syria.