GENEVA: Thousands more civilians have been killed in Ukraine during nearly 11 weeks of war there than the official U.N. death toll of 3,381, the head of the U.N. Human Rights Monitoring Mission for the country said on Tuesday.

The United Nations team, which includes 55 monitors in Ukraine, has said most of the deaths were caused by explosive weapons with a wide impact area such as missile and air strikes.

“We have been working on estimates, but all I can say for now is that it is thousands higher than the numbers we have currently given to you,” Matilda Bogner told a news briefing in Geneva, when asked about the total number of deaths and injuries.

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“The big black hole is really Mariupol where it has been difficult for us to fully access and to get fully corroborated information,” she added, referring to the port city in southeast Ukraine that has seen the heaviest fighting of the war.

Moscow denies targeting civilians and calls its invasion, launched on Feb. 24, a “special military operation” to disarm Ukraine and rid it of what it calls anti-Russian nationalists. Ukraine and the West say this is a false pretext for waging an unprovoked war of aggression.

Bogner was speaking following a trip to Ukraine last week where she visited areas around Kyiv and Chernihiv previously occupied by Russian forces.

Her team has reports of over 300 unlawful killings in settlements north of Kyiv, including Bucha, she said and expected this number to rise.

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They met a 70-year-old man who hid for more than three weeks in a basement that was so crowded he had to sleep standing up, tying himself to wooden rails to prevent himself falling over. Bogner also voiced concern that both sides were using schools as army bases, with heavy military equipment in some cases.

Her team was also investigating what she described as “credible allegations” of torture, ill-treatment and executions by Ukrainian forces against the Russian invading forces and affiliated armed groups.

“In terms of the extent of violations by Ukrainian forces, while the scale is significantly higher on the side of allegations against Russian forces, we are also documenting violations by Ukrainian forces,” she said.