Syrian sources say rebel shelling on a school killed at least seven children Sunday in the government-held part of Aleppo. Dozens of other people were reported to have been wounded by the rocket fire on the Furqan neighborhood.
On Saturday, White House National Security Adviser Susan Rice warned the Syrian government and its Russian backers they will be held accountable for the "heinous" bombings of hospitals in rebel-held portions of Aleppo.
"The United States condemns in the strongest terms these horrific attacks against medical infrastructure and humanitarian aid workers. There is no excuse for these heinous actions," she said." The Syrian regime and its allies, Russia in particular, bears the responsibility for the immediate and long term consequences these actions have caused in Syria and beyond."
Airstrikes and artillery fire carried out by government forces in Aleppo killed at least 27 people Saturday, marking the fifth straight day of bombardment of the city, which is home to more than 275,000 people.
On Friday, government bombs hit four hospitals in Aleppo, prompting the rebels' appointed health directorate to declare all hospitals in opposition-held areas out of service.
"The intentional destruction of infrastructure for survival has made the besieged steadfast people, including children, elderly and men and women, without medical facilities to treat them," the directorate said in a statement.
The Britain-based Syrian Observatory for Human Rights said Syrian warplanes bombed more than 20 neighborhoods.
Since the renewed assault began Tuesday, about 100 people have been killed, including two people killed by rebel mortars targeting government-held parts of the city, according to state media.
The freshly rekindled fighting in Aleppo comes after a brief period of calm when Russia agreed to halt its airstrikes and allow humanitarian aid into the city and fleeing residents out.
U.N. Syria envoy Staffan de Mistura is scheduled to visit Syria's capital, Damascus, Sunday to speak with Syria's foreign minister and other high-ranking military officials. The siege of Aleppo is expected to be among the topics discussed.