A Ukraine Marine commander who is trying to defend Mariupol has written a letter to Pope Francis pleading for help, declaring that the besieged city "is what hell on earth looks like." 

The desperate message from Maj. Serhiy Volyna of the 36th Separate Marine Brigade was published Monday by the Ukrainska Pravda newspaper

"You have probably seen a lot in your life. But I am sure that you have never seen the things that are happening to Mariupol," Volyna wrote. "Because this is what hell on earth looks like." 

A resident looks at a damaged apartment building in Mariupol, Ukraine, on Saturday. 

A resident looks at a damaged apartment building in Mariupol, Ukraine, on Saturday. 

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Volnya, who describes himself as Orthodox, says he believes in God and "I know that light always overcomes darkness." 

"I have not seen your appeals to the world and I have not read all your recent statements; I have been fighting for more than 50 days, completely surrounded, and all I have time for is a fierce battle for every meter of this city that is surrounded by the enemy," he said in his letter to Francis. 

"I have little time to describe all the horrors I see here every day. Women with children and babies are living in bunkers at the factory, they are hungry and cold," he continued. "Every day they are living in the sights of enemy aircraft. The wounded die every day because there is no medicine, no water, no food." 

Pope Francis delivers the traditional 'Urbi et Orbi' (To the city and to the world) blessing at the end of the Catholic Easter Sunday mass he led in St. Peter's Square at the Vatican on Sunday.

Pope Francis delivers the traditional 'Urbi et Orbi' (To the city and to the world) blessing at the end of the Catholic Easter Sunday mass he led in St. Peter's Square at the Vatican on Sunday. (AP/Alessandra Tarantino)

"I am turning to you for help. Because the time has come when prayers are not enough. Help save them," Volnya also said. "After the bombing of the drama theater, no one has any trust in the Russian occupiers anymore. Bring the truth to the world, evacuate people and save their lives from the hands of Satan, who wants to burn all living things." 

On Monday, the United Kingdom’s Ministry of Defence said "the effort to capture Mariupol has come at a significant cost to its residents.  

Ukraine Mariupol damage

A boy rides a scooter near a destroyed building in Mariupol, Ukraine, last Thursday. (REUTERS/Alexander Ermochenko)

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"Large areas of infrastructure have been destroyed whilst the population has suffered significant casualties," it said in an intelligence update. 

"Russian commanders will be concerned by the time it is taking to subdue Mariupol," the ministry added. "Concerted Ukrainian resistance has severely tested Russian forces and diverted men and materiel, slowing Russia’s advance elsewhere."