White House national security adviser Susan Rice said the United States condemned "in the strongest terms" the latest air strikes against hospitals and urged Russia, an ally of Syrian President Bashar Assad, to take steps to halt the violence.
Intense air strikes have battered the eastern part of the city since Tuesday, when the Syrian army and its allies resumed operations after a pause lasting weeks. They launched ground attacks against insurgent positions on Friday.
The war monitor, the Britain-based Syrian Observatory for Human Rights, said at least 27 people, including children, had been killed in eastern Aleppo on Saturday by dozens of air strikes and barrel bombs and dozens of artillery rounds.