The experts found signs of beating of detainees, electric shocks, forced nudity, and sex- and gender-based violence even on minors by Russian personnel.

The UN Human Rights Council (UNHRC) formed the Commission of Inquiry of Ukraine this year to investigate war crimes in Ukraine. Russian President Vladimir Putin on February 24 ordered a military invasion of Ukraine, following which Russian troops occupied large parts of Ukrainian territory where they are alleged to have carried out war crimes. Some of these territories have only been liberated this month after over six months of Russian occupation.

The UNHRC experts have so far focused on four regions – Kyiv, Chernihiv, Kharkiv, and Sumy.

Presenting their most extensive findings so far, they cited testimonies by former detainees of beatings, electric shocks and forced nudity in Russian detention facilities, and expressed grave concerns about executions in the four regions.

"We were struck by the large number of executions in the areas that we visited. The commission is currently investigating such deaths in 16 towns and settlements," said Erik Mose, the commission's chairman, adding that his team had received and was documenting "credible allegations regarding many more cases of executions".

Mose said the investigators visited 27 towns and settlements as well as graves and detention and torture centres. They interviewed more than 150 victims and witnesses and met with advocacy groups and government officials.

"Based on the evidence gathered by the commission, it has concluded that war crimes have been committed in Ukraine," said Mose, without specifying which side in the war committed the alleged crimes.

He said the team had examined two incidents of ill-treatment against Russian soldiers by Ukrainian forces.

Mose said an unspecified number of Russian soldiers were found to have committed crimes of sexual or gender-based violence. The victims ranged between 4-82-years-old.

The commission plans to gradually expand its investigation, with areas of interest including allegations of filtration camps for people being detained or deported, the forced transfer of people, and allegations of expedited adoption of children.

Ukraine has long alleged that Russia committed extensive war crimes in Ukraine. This has found acceptance in the West and US President Joe Biden has called Putin a "war criminal".?

Morever, mass graves have been discovered at multiple places in territories that were liberated by Ukrainian forces from Russian occupation, suggesting that people were killed and buried en masse under the Russian occupation – a sign of war crimes.

(With AP inputs)