Rescuers and civilians search the rubble of a destroyed building in the Syrian village of Kfar Jales, on the outskirts of Idlib, following airstrikes by Syrian and Russian warplanes on Nov. 16. (Omar Haj Kadour/AFP via Getty Images)

As Syrian government airstrikes pounded eastern Aleppo on Wednesday, people huddled around incubators in the basement of the city’s only remaining children’s hospital, waiting in silence as they counted the bombs.

By midday, they said, the tally had passed 20, shaking the ground and shattering equipment in the rooms above. Speaking from their underground refuge, the hospital’s director said he and his staffers were trapped. 

The attacks continued as night fell, marking the second day of a major offensive to retake Aleppo’s eastern districts from armed opposition groups. Defeat in Aleppo, once Syria’s economic powerhouse, would be a major blow to the rebels. It could also hasten the fall of their remaining strongholds across the country.

The offensive came a day after government forces and their Russian allies resumed attacks across northern Syria, including Russian cruise missile strikes from a warship in the Mediterranean. 

The White Helmets rescue group said at least 87 people were killed Wednesday in Aleppo province. The number is expected to rise significantly as attacks intensify and underequipped medical facilities struggle to cope.

“The planes are up above. We can’t get out,” said the children’s hospital director, who gave his name as Hatem. “We’ve been hit before, but this isn’t like the other times. Every mother is holding her child. We can’t control things anymore. The parents want to protect their children by themselves.”

Residents said eastern Aleppo’s central blood bank, located close by, also was hit. Video footage showed the aftermath of the fierce bombardment. Fires licked the edges of cars and buildings, and the air was filled with dust. 

The Independent Doctors Association, a nonprofit group that supports the children’s hospital, said it was badly damaged.

When they finally left the basement under cover of darkness, staff members at the children’s hospital found that the bombing had given way to shelling. And as nurses ushered patients back to their beds, the doctors prepared for a long night ahead. 

“We’re safe, but we have to tidy up now. This will only happen again,” said Hatem, the director. 

It was at least the ninth such attack on a medical facility in opposition-held areas nationwide in three days. The United States on Tuesday condemned the previous attacks, calling them violations of international humanitarian law.

The bombardment ended a period of relative respite, particularly in eastern Aleppo, where Moscow halted airstrikes on Oct. 18 ahead of brief cease-fires. Although residents were ordered to leave for their own safety, few did so. Many expressed fears about what awaited them outside.

Russia said Tuesday that it had launched a major offensive against rebel-held areas in Idlib and Homs provinces, but it denied involvement in the new attacks on Aleppo.

In Moscow, a spokesman for the Defense Ministry, Maj. Gen. Igor Konashenkov, said Russian warplanes have “carried out no strikes against the city of Aleppo for 29 days now,” according to the Interfax news agency.

The city of Aleppo has been split into the government-held west and the rebel-held east since 2012 along one of the most intractable front lines of the war. Eastern Aleppo is surrounded by an array of government-allied forces — including Syrian troops and Iran-backed militias — and supply routes have been cut. 

The United Nations said last week that aid workers in the area had handed out the last of their food supplies. Few families manage three meals a day, and many go to bed hungry.

“We’re suffering from the most basic needs. There’s not even fuel for ambulances,” said Najmaldin Khaled, 30, a student. “Russia has given the green light to attack Aleppo again, and there’s no solution for us on the horizon.”

On Wednesday, the state-owned TV channel Ikhabariyah reported large troop deployments along several fronts in Aleppo. It claimed an assault was imminent and “zero hour” would soon begin.

The Syrian and Russian governments have framed the fight against the armed opposition groups as a war on terrorism. In an interview with Portuguese television that aired Tuesday, Syrian President Bashar al-Assad suggested that U.S. President-elect Donald Trump could be a “natural ally” of the Damascus government if he is “genuine” about fighting “terrorists” in Syria.

But the government attacks have repeatedly targeted civilian infrastructure, often areas where moderate rebel factions operate. Assad’s troops have also laid siege to dozens of towns and villages, adopting a policy toward civilians that the United Nations has labeled “surrender or starve.”

Syria’s conflict has killed an estimated half-million people and touched off the largest refugee crisis since World War II.

Syria’s rebellion began in 2011 with peaceful protests, but it is increasingly dominated by extremist factions, including al-Qaeda-linked Jabhat Fatah al-Sham. 

The Syrian Observatory for Human Rights, a Britain-based monitoring group, said Wednesday that Russian airstrikes have resumed in Idlib, a province where the faction, formerly called Jabhat al-Nusra, operates among civilians and other rebel groups. 

Sherif al-Khalaf, a journalist from the region, said the bombing had struck 34 areas since Tuesday, killing six and wounding dozens. “The damage is immense, and people are frightened,” he said. 

Heba Habib in Stockholm and David Filipov in Moscow contributed to this report.