Liz Breuker, a former US soldier, reacts as she looks at portraits of US volunteer fighters at a makeshift memorial for the fallen Ukrainian and foreign fighters, during a memorial event for US volunteer fighters who were in Ukraine's armed forces and killed fighting against Russian troops, on the Independence Square in Kyiv on March 14, 2025. Roman Pilipey, AFP

Russia has committed the crimes against humanity of enforced disappearances and torture in its war in Ukraine -- part of a systematic attack on civilians, a United Nations investigation has concluded.

The new report by the UN's Independent International Commission of Inquiry on Ukraine, published online this week, is to be formally presented to the UN Human Rights Council next Tuesday.

"The commission has concluded that Russian authorities committed enforced disappearances and torture as crimes against humanity," the report said.

"Both were perpetrated as part of a widespread and systematic attack against the civilian population and pursuant to a coordinated state policy," it added.

The categorical nature of that statement is unusual for UN investigators.

Large numbers of civilians were detained in areas that came under Russian control, said the report. Many of them were then transferred to detention facilities in occupied Ukraine or in Russia.

The Russian authorities "committed additional violations and crimes during these prolonged detentions", it added.

"Many victims have been missing for months and years, and some died in captivity."

In addition, the authorities have systematically failed to provide information on the detainees' whereabouts.

Russia acted with the intent to remove disappeared people from "the protection of the law", said the report.

Prisoners of war have also been subjected to torture and been the victims of enforced disappearances, it added.

- Killing captured soldiers -

Russia "systematically used torture against certain categories of detainees to extract information, coerce, and intimidate", the inquiry concluded.

The most brutal forms were used during interrogations, but Russian authorities had also "systematically used sexual violence as a form of torture against male detainees".

The commission also studied a growing number of incidents concerning Russian troops killing or wounding captured or surrendering Ukrainian soldiers, which constitutes a war crime.

"Testimonies of soldiers who deserted from the Russian armed forces indicate that there is a policy not to take prisoners but to kill them instead," the report said.

Both sides had committed a war crime by killing or wounding injured soldiers using drones, it added.

The report details violations of human rights law committed by Ukrainian authorities against people accused of being collaborators.

Russia launched its full-scale invasion of Ukraine in February 2022.

The UN Human Rights Council established its highest level of inquiry in March that year to probe violations and abuses committed during the conflict.

- 'Profound scars' -

US President Donald Trump is trying to negotiate a peace deal to bring about an end to the war.

Russia on Friday said President Vladimir Putin had sent "additional" signals to Trump about a Washington-proposed ceasefire in Ukraine,  adding it was "cautiously optimistic" about the prospect of a deal.

The inquiry said that after three years of armed conflict, the "profound scars" left on its victims were increasingly visible. Many had suffered seemingly irreparable harm and endured multiple crimes and violations, it noted.

"In this context, the commission underscores again the need for justice to be done and to ensure that perpetrators of violations and crimes are held to account."

The commission said that while Ukraine had cooperated with the probe, Russia did not recognise the commission. Its requests for access, information and meetings have gone unanswered by Moscow.