Russian forces have taken captive patients and doctors in a hospital in the southern city of Mariupol, the regional governor said.
According to Pavlo Kyrylenko, Russian forces have captured 400 people and are holding them hostage in the city’s largest hospital.
The southern city has suffered some of the worst shelling during Russia’s invasion.
In a statement on his Facebook, Mr Kyrylenko relayed a first-hand account from one of the apparent hostages saying: “It is impossible to get out of the hospital. Shooting is constant and we are sitting in the basement.
“Cars haven’t been able to leave the hospital for two days. In our hospital, the Russians chased 400 people from neighboring houses. It’s impossible for us to get out."
Oleksiy Arestovich, an adviser to President Volodymyr Zelenskyy, claimed 2,500 civilians have now been killed in the city.
There are also fears of a growing humanitarian crisis as food and medical supplies have begun to run out, while Russian forces continue their attack on the city.
Ukrainian officials also accused Russian forces of blocking an aid convoy from entering the city.
The Ukrainian interior ministry said up to 20,000 had now fled the city, although many more people are waiting to escape.
The United Nations said three million people have now fled Ukraine with more than 1.8 million moving into neighbouring Poland.
As of March 15, the UN claims 691 people have been killed since Russia invaded on February 24, including 30 children.