The ferocity of the Syria conflict has only worsened, with 1,261 people killed since fighting intensified in Damascus on July 15, according to the British-based Syrian Observatory for Human Rights, which compiles reports from anti-Assad activists.

That made last week by far the bloodiest in an uprising in which activists say at least 18,000 people have been killed.

Civilians are suffering, with three-quarters of medical facilities in Damascus closed and displaced people sheltering in schools or parks, the UN refugee agency UNHCR said.

A UNHCR spokeswoman said that the number of displaced people within Syria had risen to about 1.5 million.