Russian forces struck a Red Cross facility in the besieged and destroyed southern Ukraine port city of Mariupol, Kyiv said Wednesday, where officials have warned of an unfolding humanitarian disaster.

“In Mariupol, the occupiers aimed at the building of the International Committee of the Red Cross,” Ukrainian ombudswoman Lyudmyla Denisova said in a statement on social media.

“Enemy aircraft and artillery fired on a building marked with a red cross on a white background, indicating the presence of wounded people or civilian or humanitarian cargo,” the statement said.

Denisova did not specify when the strikes had taken place and said there was no confirmation yet if anyone had been killed or injured in the attack.

Russian forces have encircled the strategic southern city and their steady indiscriminate shelling has killed at least 5,000 people, officials say, estimating total deaths could be as many as 10,000.

Aid groups have called regularly for access to Mariupol, where the conditions are described as hellish, and Ukrainian officials have accused Russian troops of forcibly deporting residents to Russia.