The bodies of 200 Mariupol residents were discovered in the basement of a building destroyed by Russian shelling, Ukrainian authorities announced Tuesday.

Adviser to the mayor of Mariupol, Petro Andriushchenko said the bodies were found in "an advanced state of decomposition" after being left under the building’s rubble for an indeterminate amount of time.

Russia forces have pummeled the city in one of the most brutal assaults in Ukraine since the war began in February.

Mariupol, Ukraine bodies found

Petro Andriushchenko, mayor of Mariupol, Ukraine, said 200 bodies were found under an apartment building that was destroyed by Russian shelling. (Petro Andriushchenko/Telegram)

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Mariupol Mayor Vadim Boichenko claimed last month that Russian troops had killed more than 20,000 residents since its invasion began, though these figures have not been verified. 

Andriushchenko said the stench of the bodies has permeated throughout an entire city block.

Mariupol city residents reportedly refused to collect the bodies after Russian backed forces implemented a series of steps residents were required to take in order to receive a "free burial."

A state-owned corporation from Donetsk (CADLR) known as Ritual, has been put in charge of exhumations and burials in the war-torn city, reported Ukrainian news outlet Pravda.

But the Russian-backed separatists required Mariupol residents to wait in line with the deceased body at a designated morgue and claim it was just "discovered," or to record a video of the body and claim it was killed by Ukrainian forces. 

Mariupol Russia Ukraine Damage

Emergency workers remove debris of a building destroyed in the course of the Ukraine-Russia conflict in Mariupol on Sunday.  (REUTERS/Alexander Ermochenko)

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According to Mariupol city officials, residents refused to comply with Russian demands and left the dead for Russian troops to deal with. 

Andriushchenko said that bodies were now being placed in bags in what has become a makeshift morgue on the street. 

"The city [has] turned into a continuous cemetery," he said. 

The majority of Ukrainians have fled the port city with an estimated 100,000 remaining behind. 

Ukrainian officials have warned that Russia will have another humanitarian crisis on its hands if it does not figure out a way to get clean drinking water to those who remain in the city. 

The lack of water, food, electricity and medical accessibility has plagued Mariupol for weeks amid Russia’s near complete destruction of the city. 

But Biochenko warned last week that Mariupol now faces an epidemiological challenge and an increasing threat of infectious disease.

Ukrainian servicemen and firefighters stand in the area outside of a maternity hospital damaged in a shelling attack in Mariupol, Ukraine, Wednesday, March 9, 2022. Associated Press journalists, who have been reporting from inside blockaded Mariupol since early in the war, documented this attack on the hospital and saw the victims and damage firsthand. They shot video and photos of several bloodstained, pregnant mothers fleeing the blown-out maternity ward, medics shouting, children crying. (AP Photo/Evgeniy Maloletka)

Ukrainian servicemen and firefighters stand in the area outside a maternity hospital damaged in a shelling attack in Mariupol, Ukraine, Wednesday, March 9, 2022.  (AP Photo/Evgeniy Maloletka)

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"The city is on the brink of summer. And summer time requires more water," he said. "The fact that today the drainage is not working in Mariupol. The sewage is not working."

It is unclear what Moscow’s plans are for the besieged city now that it has fallen to Russian forces.