STORY: "Based on the evidence gathered by the Commission, it has concluded that war crimes have been committed in Ukraine," Erik Mose told the Geneva-based Human Rights Council.
He did not say explicitly who had committed the crimes but the commission's work was focused on areas of Ukraine previously occupied by Russian forces such as Kyiv, Chernihiv, Kharkiv and Sumy.
Investigators from the commission, which was created by the U.N. Human Rights Council in March, visited 27 places and interviewed more than 150 victims and witnesses.
The commission found a large number of executions in the areas it visited including bodies with tied hands, slit throats and gunshot wounds to the head, Møse said.
He added that the investigators had identified victims of sexual violence aged between four and 82 years old. Children have been raped, tortured and unlawfully confined, he said.
Russia was called on to respond to the allegations at the council meeting but its seat was left empty. Russia regularly denies deliberately attacking civilians during what it calls its "special military operation" in Ukraine and has said in the past that accusations of human rights abuses are a smear campaign.