Bombing in Aleppo puts another major hospital out of service

Doctors at the facility, known as M10, said the assault involved cluster munitions, barrel bombs and incendiary weapons, prompting mass panic and appeals for help.

"The hospital is being destroyed. SOS, everyone," said Mohammad Abu Rajab, the hospital's administrator and radiologist, in an audio message sent to journalists Saturday morning.

As a coalition of mostly Shiite militias gathers on the outskirts of the city, hospitals in rebel-held Aleppo have endured a barrage of attacks by allied Syrian and Russian warplanes.

The attacks are apparently aimed at forcing the surrender of an area that has held out through four years of war - a full takeover of Aleppo would represent the largest military victory for Syrian President Bashar Assad since the crisis began in 2011.

"When you destroy a hospital or kill a doctor, that's a death sentence to the people around them," said Adham Sahloul, a spokesman for the Syrian American Medical Society. Only 35 doctors remain in the area, according to the World Health Organization, and attacks on medical facilities have crippled their ability to cope in the face of a blitz.

Russian and regime warplanes have dropped almost 2,000 bombs in less than two weeks, pushing Washington and Moscow's already-fragile diplomatic dance to the edge of failure. The Obama administration threatened Wednesday to cut ties over Syria altogether, but provided no indication of when it would do so or whether an alternative strategy might follow.

According to the WHO, 338 people been killed in eastern Aleppo since a cease-fire deal between the two sides was shattered by a Russian and regime attack on a United Nations aid convoy.

While U.S. Secretary of State John Kerry has attempted to tamp down that violence, his negotiating powers have been hamstrung by the White House's reluctance to engage more deeply in Syria.

In a meeting with Syrian civil society representatives on the sidelines of last month's U.N. General Assembly meeting in New York, Kerry said he had "lost the argument" on backing diplomacy with the serious threat of military force.