By Stephanie Nebehay

GENEVA, (Reuters) – Thousands of civilians could have been killed in Mariupol, a besieged city in south Ukraine, since the bombing started four weeks ago. This was according to the U.N. Human Rights Mission’s head, who told Reuters Tuesday that the first estimate.

According to a spokesperson for Mayor Vadym Biichenko, nearly 5,000 persons, including 210 children have been killed in Mariupol, which was under Russian siege a month back.

According to his office, 90% of Mariupol’s buildings were damaged or destroyed. This includes hospitals, schools and kindergartens.

Matilda Bogner (head of U.N.’s human rights mission to Ukraine), said that she believes there may be thousands of deaths in Mariupol, and also civilian casualties.

According to her, the mission does not know exactly how many people will be affected but is still gathering information.

According to witnesses, 300 were among those killed by the bombing on a Mariupol theater where they were staying. Local officials last week claimed that this was an estimate based upon local authorities.

According to a statement, U.N. human Rights office confirmed Tuesday that 1,179 civilians were killed and 1,860 had been injured in Ukraine during the conflict. This was despite reporting delays caused by hostilities.

Bogner said last week at a briefing U.N. monitors received more information on mass graves found in Mariupol. This included one believed to have 200 corpses.

Bogner stated Tuesday that “on the mass graves we have decided to call it ‘improvised’.”

She explained that the phrase “mass graves”, which may refer to victims of crime, could be used to describe people who died in Mariupol from various causes.

She said that civil casualties in conflict were thought to have been a small percentage of the bodies found in improvised graves at parks and gardens.

She said that there were some natural deaths which weren’t brought to individual or communal tombs because of the hostilities. Other people died without ever reaching doctors.

She said that it was unclear if military casualties were buried in these improvised burials.

Robert Mardini was the director-general of the International Committee of the Red Cross. He told Reuters that he had not received any firsthand information about the victims of the Mariupol theatre attack.