Civilians buried under the wreckage after air strike on makeshift field hospital

Ukrainian soldiers said the Azovstal plant, where the remaining defenders in the devastated southern city are holed up with hundreds of civilians, came under a heavy night-time attack.

They released video footage showing what appeared to be an underground hospital with debris strewn across the floor.

It showed a man in a head torch desperately trying to clear debris with a trowel, and patients with bandaged legs and arms who appeared dazed.

As people sat together, hunched on the floor in darkness, one man appeared to be praying.

Another’s hand gripped his water bottle like a vice but shook violently as it did so.

A message accompanying the footage, from the far-right Azov Brigade, said: “Attention. All night on the military field hospital, located on the territory of the plant ‘Azovstal’ in Mariupol and where the wounded defenders are, the Russians massively dropped heavy bombs capable of breaking through any concrete defensive structures.”

One soldier in the plant, Vladislav (22) said: “All hell begins at night.

"Earlier, a bomb was dropped on our hospital, where the wounded civilians and military were lying. There are many victims. There are blockages, dust and many wounded.”

Russian forces have been pummelling the steelworks factory after laying siege to the port city for weeks.

A senior US defence official said there were indications some Russian forces were now leaving Mariupol and moving towards the north-west, but fighting in the city continued.

The local governor said the invading Russian troops were preventing injured fighters from being taken out of the steelworks.

The US, meanwhile, accused Moscow of a plan to shut down Ukrainian democracy by dissolving local government then staging fake independence votes to justify its conquest.

A US official said the Kremlin may be preparing “sham referenda” in areas it seized.

In a separate video, a commander in the Azovstal plant said he had 600 injured and no medicine to treat them.

Major Serhiy Volyna, commander of Ukraine’s 36th Marine Brigade, said: “Here with us are civilians, hundreds of them. There are dozens of children. There are many people with limited physical abilities, elderly people.

“Save the Mariupol garrison. Provide us with the extraction procedure. Today is not 1940. It is 2022. People here will simply die, the injured will die.”

In a phone call, he told Sky News the field hospital operation room had been destroyed and they could no longer operate on the injured.

He described the situation as “critical” and “simply horrible”.

“I can say that the city is beyond the brink of a humanitarian catastrophe,” he said.

“It has been totally erased from the face of the Earth.”

Apart from the steelworks, the Russians held the rest of the city and were destroying infrastructure using air strikes and tanks, he said.

He appealed for an extraction of those in the steel plant to a safe third country.

According to Mariupol city council, civilians were now facing outbreaks of cholera and dysentery. The central water supply and sewage systems were not working.

Petro Andryushchenko, an aide to the mayor, said: “Air attacks on Azovstal are not subsiding.

"No ceasefire, but attempts to storm again and again. Despite the statements [by Putin].”

Local officials said much of Mariupol has been destroyed in weeks of Russian bombardment, and about 100,000 civilians are still in the city.

Many previous efforts to arrange a ceasefire to allow residents to leave have broken down. (© Telegraph Media Group 2022)