BEIRUT — Airstrikes and artillery killed more than 60 people in the past 24 hours in Aleppo, including dozens at a hospital in a rebel-held neighborhood, as Syria's largest city was turned once again into a major battleground in the civil war, officials said Thursday.
Aid agencies warn that Aleppo is on the brink of a humanitarian disaster with the collapse of a two-month cease-fire and stalled peace talks.
The intensified violence — by far the worst since the partial cease-fire began — coincides with reports of a military buildup outside Aleppo that many fear is a prelude for a government attempt to force a complete siege of the city's neighborhoods.
Battle-hardened residents were shocked by the bloodshed. Opposition activists accused the government of carpet-bombing rebel-controlled areas, while Syrian state media said more than 1,000 mortar rounds and rockets were fired at government-held districts, killing 22 people.
Video posted online by opposition activists showed rescuers pulling bodies from shattered buildings in the rebel neighborhoods of Sukkari, Kallasa and Bustan al-Qasr.
In one scene, a building's staircase hung sideways and old men were sobbing.
"The walls, cupboards, everything fell on top of them," cried one man. In another, a clearly terrified small girl with pigtails wept silently while held by a man.
A blond girl walked from the rubble behind her mother, questioning why they were bombed. "What have we done?" she cried.
In the rebel-held Sukkari neighborhood, 27 people died as a well-known field hospital supported by Doctors Without Borders and the International Committee for the Red Cross was hit overnight, along with nearby buildings, according to opposition activists and rescue workers.
U.N. envoy for Syria Staffan de Mistura appealed to the U.S. and Russia to help revive the peace talks and cease-fire, which he said "hangs by a thread."
However, the violence only escalated.
Chief opposition negotiator Mohammed Alloush blamed the government of President Bashar Assad for the violence, saying it shows "the environment is not conducive to any political action."
"What is happening is a crime of ethnic and sectarian cleansing by all means," Alloush told The Associated Press, adding it was an attempt by Assad's government to drive residents from Aleppo.
But a citizen journalist said there was little sign of people fleeing the city.
"Where can they go?" said Bahaa al-Halaby.
A Damascus-based Syrian military official denied the government had hit the hospital. The official spoke on condition of anonymity because he was not authorized to talk to the media.
Russian Defense Ministry spokesman Maj. Gen. Igor Konashenkov also denied bombing any hospitals in Aleppo, saying its aircraft have not flown any missions in the region for several days.
Col. Steve Warren, the spokesman for the U.S.-led campaign against the Islamic State group, said fighter jets from the international coalition have not carried out any airstrikes in Aleppo in the past 24 hours.
About 200 civilians have been killed in the past week in Syria, nearly half of them around Aleppo.
With the U.N.-sponsored peace talks in Geneva completely deadlocked, Syrians are watching the escalating violence with dread, fearing that Aleppo is likely to be the focus of the next, more vicious phase of the 5-year-old war.
The hospital that was hit in Sukkari has been one of the main medical centers for Aleppo since the city became divided in 2012.
Among the 27 dead were 14 patients and staff, including three children and six employees, officials said. A dentist and one of the last pediatricians in opposition-held areas of Aleppo were among the victims. The toll was expected to rise.
The 34-bed, multistory hospital, the area's main pediatric care center, was "hit by direct airstrike," according to a statement by Doctors Without Borders, also known by its French acronym MSF.
The hospital had an emergency room, an intensive care unit and an operating room, and its eight doctors and 28 nurses offered services such as obstetric care, outpatient and inpatient treatment, the MSF said. The group has supported the hospital since 2012.
The 250,000 people still in Aleppo will now have to find an alternative facility for care, said Sam Taylor, who is Syria communications coordinator for MSF and is based in Amman, Jordan.
"We're absolutely appalled," he told AP.
Dating to the 1990s, the hospital was renamed for one of the uprising's early victims, Basel Aslan, after the area came under rebel control. Aslan had been detained by security forces and tortured to death, said civil defense volunteer Ibrahim Alhaj.
The civil defense, also known as the White Helmets, said the hospital and adjacent buildings were struck in four consecutive airstrikes.
Video posted by the White Helmets showed lifeless bodies, including children, being pulled from a building and loaded into ambulances amid screams and wailing. Distraught rescue workers tried to keep away onlookers, apparently fearing more bombs.
Shortly after midday Thursday, new airstrikes in rebel-held areas killed at least 20 people in two neighborhoods, the Syrian Civil Defense and the Observatory said.
Videos by activists showed dust and smoke rising from burning buildings as men and women ran from collapsing houses and children cried, looking for their parents.
Syrian lawmaker Omar Ossi, part of the government delegation at the Geneva talks, blamed the escalation on Turkey and Saudi Arabia as patrons of the rebels.
"The Syrian army will be able to regain the initiative and rein in this Turkish interference," he said.
Humanitarian officials said the fighting is putting millions at grave risk.
The U.N. won't be able to reach embattled Syrians if the intensified violence continues on and near aid convoys, said Jan Egeland, an adviser to the U.N. envoy, adding that in the last three days, one convoy into Homs was hit by a mortar round and another had to stop several times due to air raids.
Egeland decried a "catastrophic deterioration" of the security situation in Aleppo, saying a lifeline for hundreds of thousands of Syrians "may be broken."
The ICRC said stocks of contingency food and medical aid are expected to run out soon and warned that an escalation in fighting means that they cannot be replenished.
The partial cease-fire that began Feb. 27 held for weeks. Formally called a "cessation of hostilities," it was never meant to be a total truce because it excluded extremists such as the Islamic State group and its rival al-Qaida branch, the Nusra Front.
It frayed further recently as casualties mounted, particularly in Aleppo and other parts of northern Syria. Airstrikes this week hit a training center in rural Aleppo for the Syrian Civil Defense, killing five volunteers.
Since April 19, nearly 200 people have died, including 44 in an airstrike on a market in a rebel-held area in northern Syria's Idlib province. Dozens of civilians also were killed by rebel shelling in government-held areas. There also has been shelling in Damascus, along with a car bombing — both rare for the capital.
De Mistura, the U.N. envoy, told the Security Council via videoconference that after 60 days, the truce "hangs by a thread."
"I really fear that the erosion of the cessation is unraveling the fragile consensus around a political solution, carefully built over the last year," he said. "Now I see parties reverting to the language of a military solution or military option. We must ensure that they do not see that as a solution or an option."
The talks foundered last week after the main opposition group, called the High Negotiating Committee, suspended its formal participation to protest alleged cease-fire violations by the government, a drop in humanitarian aid deliveries and no progress in winning the release of detainees.
Associated Press writer Zeina Karam in Beirut and Albert Aji in Damascus, Syria, contributed to this report.