DAMASCUS, Syria-The Syrian army and rebels unleashed deadly new attacks on each other Friday in Aleppo, with insurgents shelling a mosque during weekly prayers and government airstrikes hitting opposition neighborhoods in escalating bloodshed the U.N. decried as a "monstrous disregard for civilian lives by all parties."
More than 200 people have been killed in eight days of mounting violence in and around the contested northern city, including 15 at the Malla Khan mosque hit by rebel rockets and another 10 from the government warplanes and helicopters, officials said.
The surge in fighting has caused the collapse of a two-month cease-fire brokered by the U.S. and Russia. It also has raised fears of an all-out government assault on Aleppo and warnings of a humanitarian disaster in the 5-year-old civil war.
In rebel-held neighborhoods, medical facilities, bakeries and a water station have been pounded by a government bombardment, residents say. Electricity is down to a few hours a week. A single road out of Aleppo is the only supply line for the insurgent-controlled districts, where an estimated 250,000 people remain. If forces loyal to President Bashar Assad take the road, there could be major shortages of food and medicines.
"People have already started fleeing the city," said Baraa al-Halaby, an activist who watched older men, women and children leave his rebel-held neighborhood Friday. "If Aleppo comes under siege, people will starve to death within a month."
Assad's military declared a brief truce in the capital of Damascus and its outskirts and the coastal province of Latakia-but not in Aleppo.
That could signal plans for a ground assault. Pro-Assad media in Lebanon have been reporting for weeks that reinforcements are preparing for the "grand battle of Aleppo."
Syria's largest city and its commercial center before the war, Aleppo has been divided between the two camps. Now it is once more the main battleground after peace talks stalled in Geneva.
Zeid Ra'ad Al Hussein, the U.N. High Commissioner for Human Rights, said the latest fighting showed a "monstrous disregard for civilian lives by all parties to the conflict."
In a statement released in Geneva, Zeid urged the sides to step back from a return to all-out war.
"In short, the violence is soaring back to the levels we saw prior to the cessation of hostilities. There are deeply disturbing reports of military buildups indicating preparations for a lethal escalation," he said.
Russian Foreign Minister Sergey Lavrov and U.S. Secretary of State John Kerry discussed ways to resolve the Syrian conflict through the "preservation and strengthening" of the Feb. 27 cease-fire, the provision of humanitarian assistance to people living in blocked areas and the establishment of a sustainable political process, the Foreign Ministry said in a statement.
Lavrov again stressed the need for the full participation of Syrian Kurds in the talks, as well as for the disengagement of the moderate opposition from groups considered to be terrorist organizations.
U.S. State Department spokesman Mark Toner said the two "talked about the cessation of hostilities; about some of the efforts that are under way; about the reinforcement of that cessation of hostilities in parts of Syria; and also about the political negotiation track as well."
After a brief lull overnight, government airstrikes resumed Friday morning on rebel-held areas. At least 10 people died and dozens were wounded, according to the Local Coordination Committees and Bibars Mishal, a volunteer with the first-response Civil Defense Teams in Aleppo. The Syrian Observatory for Human Rights, a Britain-based group that monitors the conflict, put the death toll at 11.
The rebel rockets struck the Malla Khan mosque after noon in the government-held Bab al-Faraj districts, killing 15 and wounding 30, state TV reported.
In opposition areas, air raids prompted religious leaders to suspend the collective Friday prayers in mosques for the first time.
"The heart of the believers is aching but preserving lives is an important religious duty," the Religious Council of Aleppo, an opposition body that runs religious affairs, said in an online statement.
Government airstrikes have heavily damaged infrastructure in opposition neighborhoods. A main hospital supported by Doctors Without Borders was bombed late Wednesday, and the death toll from that attack rose Friday to more than 50, according to the group, known by its French acronym MSF. Among the dead were patients and at least six staff, including one of Aleppo's remaining pediatricians.
The hospital was one of the few standing medical centers in Aleppo and offered pediatric and cardiology wards.
A clinic was damaged Friday in the neighborhood of al-Marj, but there were no casualties, said two opposition monitoring groups. A water distribution point in Bab al-Nairab was damaged Wednesday, depriving four neighborhoods of drinking water, said Mishal, the civil defense volunteer. He called eight days of government airstrikes "vicious, vicious, vicious."
A third medical center in the Bustan al-Qasr neighborhood was bombed shortly before dark Friday, destroying the facility. No one was at the facility at the time, but three bystanders were killed.
MSF said it was "desperately" worried that people in rebel-held areas of Aleppo are in danger of being cut off from medical care.