"The risk of cholera is very high, like red, red level," Petro Andriushchenko, an advisor to Mariupol’s mayor, told ABC News, APA reports.

He added that the municipality could not provide an estimation of the number of infected cases due to a lack of proper access to the occupants amid the occupation by Russian forces.

While the warnings have intensified in the past few days, Mariupol Mayor Vadym Boychenko said on Telegram last month that due to problems with water supply, the city is threatened by an infectious catastrophe and more than 10,000 people may die by the end of the year.

The warming spring and summer weather will likely increase transmission, the report said.

"The weather is hot. There are still dead bodies on the streets of the city -- especially under the debris of residential buildings. In some blocks, it is impossible to walk by -- due to the stench of rotten human flesh. There was no rain for a while, and it is getting hotter," a resident of Mariupol, who did not want to be named for security concerns, told ABC News.