Ukrainian officials issued dire warnings today about the fate of civilians and the last fighters in Mariupol after weeks of Russian bombardment.

The invading forces have continued to attack the southern port city's Azovstal steelworks, now the last bastion of Ukrainian defenders who have been under siege since the war began.

"Azovstal is on fire again after the bombing. If there is hell on earth, it is there," Petro Andryushchenko, an aide to Mayor Vadym Boichenko, wrote on Telegram.

The Azov Regiment holed up inside it released new photos of some of its injured soldiers today. They said Russia was bombing the factory from the air and trying to storm it.

Amputations have taken place due to a lack of antibiotics in the steelworks

Human rights ombudswoman Lyudmyla Denisova appealed to the United Nations and Red Cross to help evacuate wounded fighters holed up in the vast steel works.

She said the destruction of a makeshift hospital there meant many were dying.

"The aggressor does not give the wounded military a chance to survive," she wrote on Telegram.

"Due to the risk of infection because of a lack of antibiotics, medical instruments and sterile dressings, doctors are forced to amputate the limbs (of the wounded) even with minor injuries."

An injured fighter flashes the victory sign

Reuters could not verify the conditions in the sprawling Azovstal steelworks or the reported destruction of the underground hospital earlier this week.

Russia, which denies targeting civilians, did not immediately comment on Ms Denisova's statement.

She said there were hundreds of wounded among the more than 1,000 fighters estimated to still be in the steel works. The numbers could not be confirmed independently.

Meanwhile, the wives of two of the last remaining Ukrainian fighters holed up in the steelworks met Pope Francis today at the end of his audience in St Peter's Square.

They asked him to help persuade Russia to let them be evacuated.

"You are our last hope, I hope you can save their lives, please don't let them die," Kateryna Prokopenko, 27, could be heard telling the pope on a video released by the Vatican.

Kyiv says it is likely that tens of thousands of people have been killed in Mariupol since Russia invaded Ukraine on 24 February.

Food, water, power and heating supplies were cut off in the city weeks ago.

Mariupol was home to more than 400,000 people before the war but is now an urban wasteland.

"The (Russian) occupiers have turned Mariupol into a medieval ghetto," Mayor Boichenko, who has left the city, said on national television.

"Without medicine and medical care, the restoration of the water supply and proper sewerage in the city, epidemics will erupt.

"Today, the majority of the current population is old and sick. Without proper conditions, mortality among vulnerable groups will increase exponentially."