But in the past two weeks Russian forces have repeatedly struck medical facilities in Ukraine, prompting claims they are being systematically targeted, despite Russian denials.

According to the World Health Organization (WHO), there have been 24 verified attacks on health care facilities in Ukraine so far.

“These attacks have led to at least 12 deaths and 17 injuries. At least 8 of the injured and 2 of the killed were verified to be health workers. The attacks took place between 24 February and 8 March,” WHO said Thursday.

“WHO strongly condemns these attacks. Attacks on health care violate international law and endanger lives. Even in times of conflict, we must protect the sanctity and safety of health care, a fundamental human right,” it said in an email to CNN.

A CNN crew in Mykolaiv, in southern Ukraine, saw patients — including sick children — take cover in a hospital’s underground bomb shelter as air raid sirens wailed.

Stass, 12 years old and heavily bandaged, was unaware that his father was not with him in the hospital at that moment because he was burying the boy’s mother and sister. “I was in the neighbor’s basement when the bomb hit the roof on my side,” he said. “We ran to my granny’s house. Another hit there. My arm is broken. My dad and neighbor brought me here. I was in a coma for two days.”

In a late-night video address Wednesday, Ukrainian President Volodymyr Zelensky denounced the Mariupol hospital bombing as an “atrocity” and “proof of a genocide of Ukrainians,” as he renewed his calls on Western leaders to establish a no-fly zone over Ukraine.

He also called on Russia to explain why it was carrying out strikes on hospitals. “Why were they a threat to the Russian Federation? What kind of country is the Russian Federation that is afraid of hospitals, afraid of maternity wards and destroys them?” he said.

Russian Foreign Minister Sergey Lavrov on Thursday alleged without evidence the bombed hospital in Mariupol was the radical Azov battalion’s base and that all patients and nurses had left. Later on Thursday, a Russian Ministry of Defense spokesperson denied in a briefing that Russia had shelled the maternity hospital at all, calling it a “provocation.”

Lavrov said Russia informed the UN Security Council meeting about this a few days before the attack. The Azov battalion is integrated into the Ukrainian armed forces but was formerly an independent ultra-nationalist militia.

“On March 7 or 6, I don’t remember exactly now, but at the meeting of the UN Security Council, our delegation presented facts that this maternity hospital had long been captured by the Azov battalion and other radicals,” Lavrov said.

“All the women in labor, all the nurses, in general, all the staff was driven out of there,” Lavrov added.

Video from the hospital after the bombing clearly showed there were both patients and staff there, including pregnant women.

A ‘dire and desperate’ situation

The Mariupol hospital attack has sparked a flurry of international condemnation, with French government spokesperson Gabriel Attal calling it “inhumane” and “unjustifiable” in comments Thursday.

“I want to say in the name of the French government that the strike by Russia against Mariupol’s pediatric hospital was inhumane and cowardly. It’s women, children, healthcare workers who were targeted, it’s unjustifiable,” he said in an interview with French radio station RTL.

Calling again for a ceasefire in Ukraine, Attal predicted the worst was yet to come in the Russian invasion of Ukraine.

UK Prime Minister Boris Johnson also condemned the strike in Mariupol, saying: “There are few things more depraved than targeting the vulnerable and defenseless.”

The United Nations said it was following up “urgently” on “shocking reports” of the bombing of the hospital.

“It bears reminding that we have called, WHO has called for an immediate halt to attacks on health care, hospitals, health care workers, ambulances — none of these should ever, ever be a target,” UN spokesman Stephane Dujarric said Wednesday.

The humanitarian crisis in Ukraine “continues to deteriorate rapidly,” Dujarric added. More than 2.2 million people have crossed international borders escaping Ukraine since the invasion began, Dujarric said.

In Mariupol itself, the situation is becoming “increasingly dire and desperate,” the International Committee of the Red Cross (ICRC) said Thursday.

It warned that “hundreds of thousands of people have no food, water, heat, electricity, or medical care,” and said that “people urgently need respite from violence and humanitarian aid.”

“All the shops and pharmacies were looted four to five days ago. Some people still have food but I’m not sure for how long it will last,” the deputy head of sub-delegation of ICRC Sasha Volkov said in a interview recorded Wednesday and published on the ICRC website.

Many people in Mariupol have reported having no food for children, Volkov said. “People started to attack each other for food. People started to ruin someone’s car to take the gasoline out.”

At least 1,300 civilians have been killed in Mariupol since the Russian invasion began, an adviser to the city’s mayor said Wednesday. CNN cannot independently verify these casualty figures.

Zelensky warned Russian propagandists they “will be held responsible for complicity with war crimes” in a video message Thursday.

“Russian citizens will hate you for consistently lying to them for many years. When they will feel the consequences of your lies, feel with their wallets, their dwindling opportunities, with the stolen futures of the Russian children,” he said, adding that the aggressor also pays a price in war.

His warning came after Ukrainian Prosecutor General Iryna Venediktova on Wednesday called for a “new model” of investigative efforts to tackle alleged war crimes in Ukraine.

And for those trying desperately to flee Russian attacks, evacuation efforts continue to be fragile and fleeting. Efforts to evacuate thousands of civilians trapped in Mariupol have so far been thwarted. Ukrainian officials have accused Russian forces of violating agreed pauses in hostilities.

The Ukrainian government said Thursday it was opening evacuation corridors in several parts of the country. As of 10 a.m. local time it was unclear whether the corridors — designed to allow civilians to escape to safer regions — had been agreed with Russia or international humanitarian agencies.

Meanwhile, a meeting between Ukrainian Foreign Minister Dmytro Kuleba and Lavrov in Turkey ended Thursday without an agreement reached on evacuation corridors or a ceasefire, Kuleba said.

At a news conference following the meeting, Kuleba said he had raised the prospect of establishing a corridor to allow civilians to flee from the besieged city of Mariupol but “unfortunately Minister Lavrov was not in a position to commit himself to it.”