The Azovstal steel plant is the last part of Mariupol that is still held by Ukrainian fighters who have vowed to stay put despite offers of surrender. A video emerged of the stuck soldiers singing in the bunker as there is shelling above by Russian forces.
A video of a 21-year-old soldier singing resistance songs from the Second World War in the darkened bunker was posted on social media.
She sang: “Be faithful to your Motherland until death. For us, Ukraine is above all.”
Lieutenant Colonel Prokopenko said on the Telegram app: “The situation is extremely hard. However, we will continue carrying out the order to keep up our defences no matter what.
“I am proud of my soldiers who are making superhuman efforts to contain the pressure of the enemy.”
A Mariupol mayoral aide Petro Andryushchenko wrote on Telegram: “In addition to the military, at least 100 civilians remain in the (Azovstal) shelters.
“However, this does not reduce the intensity of attacks by the occupiers.”
Colonel Prokopenko’s wife, Kateryna Prokope said: “We don’t want them to die, they won’t surrender. They are waiting for the bravest countries to evacuate them.
“We won’t let this tragedy happen after this long blockade. We need to evacuate our men.”
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On Wednesday, some of the wives of the soldiers stuck in the bunkers approached the Pope explaining their fears of their husbands’ deaths or torture if captured.
With little chance of survival, the troops are also battling low food, water and medical supplies and some of the injured suffering from gangrene.
Yuliia Fedusiuk, 29, whose husband Arseniy Fedusiuk is in the Azovstal complex, said: “They will not go to Russian captivity because they will be tortured and killed.”
She added that her husband had asked her to do research online about how to survive without water.
She added: “We asked the Pope to help them, to be a third party in this war and to let them go through the (humanitarian) corridor.
“He told us that he prays for us and that he is doing everything he can.”
Ms Prokopenko, 27, told Francis: “You are our last hope. We hope you can save their lives. Please don’t let them die.”
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Speaking with journalists she added: “We asked him to come to Ukraine, to talk to Putin, to tell him ‘Let them go’.
“He just said he would pray for us. We hope that this meeting will just give us the chance to save their lives.”
The Pope has previously requested an audience with Putin in an attempt to negotiate the end of fighting, but he received no reply.
Pope Francis has condemned the war but not the Russian forces as the Holy See always has to maintain neutrality during war time which, according to the Vatican, is “not out of cowardice or an excess of diplomatic prudence, but in order not to close the door, in order to always leave open a crack to the possibility of stopping the evil and saving human lives”.