The U.N. special envoy to Syria, Staffan de Mistura, warned at a news conference in Geneva Thursday that a humanitarian disaster was unfolding in Syria with increased fighting in Aleppo and three other locations.
Al Quds field hospital, situated in a rebel-held neighborhood in Aleppo, was hit by a missile from a fighter jet Wednesday, witnesses said. It's unclear for which side in the conflict the fighter jet was flying.
The Syrian Observatory for Human Rights said that 27 people were killed at the hospital, including at least three children and three doctors. A civil defense worker at the scene also reported that the death toll was 27.
The hospital strike came amid an increase in violence around Aleppo, a key city in northern Syria, and other regions, despite a nationwide "cessation of hostilities" technically being in force.
UN's top envoy to Syria, Staffan de Mistura, is urging Russia and the U.S. to revive peace talks.
At least 148 civilians have been killed in Aleppo in the past six days, according to the Observatory.
Speaking in Geneva, de Mistura urged the United States and Russia to help revive peace talks, saying the truce was barely holding and "hangs by a thread."
"In the last 48 hours, we have had an average of one Syrian killed every 25 minutes, one Syrian wounded every 13 minutes," he said.
Jan Egeland, chair of the U.N. task force on humanitarian access in Syria, said that there had been a "catastrophic deterioration" in Aleppo and parts of Homs over the past day or two.
He said that if strikes continued, the U.N. would not be able to carry out a planned delivery of aid to 35 besieged locations.
"I can't express how high the stakes are for the next hours and days," he said.
'Brink of humanitarian disaster'
Al Quds hospital was supported by both Doctors Without Borders, which uses its French acronym, Médecins Sans Frontières (MSF), and the International Committee of the Red Cross (ICRC).
MSF's head of mission for Syria, Muskilda Zancada, said the organization condemned the "outrageous targeting of yet another medical facility" in the country.
"This devastating attack has destroyed a vital hospital in Aleppo, and the main referral center for pediatric care in the area. Where is the outrage among those with the power and obligation to stop this carnage?" she said in a statement.
According to hospital staff, the facility had been reduced to rubble by a direct strike from the air.
The 34-bed hospital, staffed with eight doctors and 28 nurses, had an emergency room, obstetric care, an outpatient department, an inpatient department, an intensive care unit and an operating theater, MSF said in a statement.
The organization had been donating medical supplies to the facility since 2012.
Among the victims was one of the last few pediatricians in Aleppo, the group's U.S. executive director Jason Cone tweeted.
Marianne Gasser, head of the ICRC mission in Syria, also condemned the attack on the hospital, saying Aleppo was being "pushed further to the brink of humanitarian disaster."
"The recent attack on the ICRC-supported Quds hospital is unacceptable and sadly this is not the first time the lifesaving medical services have been hit," she said.
"We urge all the parties to spare the civilians. Don't attack hospitals, don't use weapons that cause widespread damage."
The ICRC said it had been supporting most of the medical facilities on both sides of Aleppo's front line by providing medicines, equipment and clean water.
Intense fighting
The same month, President Bashar al-Assad's regime had cut off access to the main road from Aleppo to the Turkish border, hampering movement of rebels fighting his government and aid agencies trying to bring supplies to the city.
Years of conflict
Syria's conflict started in 2011 and has raged on for years, with more than 250,000 killed, according to the United Nations.
Government forces fired on the protesters, killing scores. As the government crackdown intensified, the opposition got more organized.
CNN's Nic Robertson, Lindsay Isaac and Milena Veselinovic contributed to this report
