The head of the United Nations human rights team in Ukraine said on Friday that monitors had received fresh information regarding mass graves in Mariupol, including one that seemed to hold 200 victims.

“We have got increasing information on mass graves that are there,” according to Matilda Bogner, who spoke to media via video link from Ukraine, some of the proof came from satellite photographs.

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She did not go into additional detail about the evidence, just saying that it was unclear whether the fatalities were troops or civilians.

Since Russia’s invasion on Feb. 24, the United Nations Human Rights Office, which has 50 workers in the country, has recorded 1,081 civilian deaths.

However, due to verification issues, the toll includes “very few” from Mariupol, which has been under heavy bombardment for weeks and is virtually shut off from any communication, according to Bogner.

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“The extent of civilian casualties and the extent of damage raises serious concerns and suggests strongly there have been violations of international humanitarian law and in particular of indiscriminate attacks,” she said.

On Sunday, a Reuters journalist who arrived in a sector of Mariupol held by Russian forces observed several bodies lying by the road and a group of men digging graves in an area of grass by the roadside.

Bogner’s team is investigating allegations of human rights violations, including reports that Russian soldiers shot and murdered civilians fleeing in their cars; dozens of cases of disappearances of Ukrainian officials and journalists; and the forced relocation of civilians into Russian-held area.

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Its work will be aided by the establishment of a new commission of inquiry, which was approved by the Geneva-based Human Rights Council earlier this month. Three human rights experts will be chosen “in the coming days,” according to a Council official on Friday.

Russia, which has described its actions in Ukraine as a “special operation” since February 24, has denied targeting civilians. According to Russian news agencies, buses transported hundreds of “refugees” from Mariupol to Russia.

Bogner also stated that her team has received claims of violations by Ukrainian forces, including indiscriminate bombardment in Donetsk, eastern Ukraine, and two alleged killings of civilians because of their apparent sympathy for Russia.

Ukrainian officials have stated repeatedly that they have never targeted civilians, and that the people in Donetsk and Luhansk are Ukrainians.