The Latest: War in Ukraine: Senators Ask U.S. to Share Evidence of War Crimes With I.C.C.

In one case shared in the report, a Ukrainian officer was killed by Russian forces during the siege of the city of Mariupol last year after he refused, under torture, to disclose the password for a military radio channel.

The execution of prisoners is only one facet of the atrocities committed since Moscow launched its full-scale invasion of Ukraine last February. Mass killings of civilians by Russian troops outside the capital during their occupation of the area galvanized anger at Moscow within Ukraine and internationally. Evidence of torture, rape and other atrocities have been uncovered in many places that were occupied by Russian forces but have since been recaptured.

U.N. investigators found that Russian forces regularly tortured or beat Ukrainian prisoners of war before they were interned to extract information, to humiliate them or as a form of retribution.

The forms of torture recorded included “beating, electrocution, or, in several cases, being shot or stabbed in the legs,” Matilda Bogner, the head of the U.N. Human Rights Monitoring Mission in Ukraine, said at a briefing in Kyiv. “Mock executions were also common. The report describes one case where a prisoner of war died from injuries within hours after he was tortured.”

Almost half of the 229 Russian prisoners interviewed said they had been tortured or ill-treated shortly after capture, or during interrogation, and prisoners of war were beaten, shot in the legs, electrocuted and subjected to mock executions and other threats, she said, adding that there were fewer reports of mistreatment once prisoners were in pretrial detention or in Ukrainian prisoner-of-war camps.

“Our job is not to compare” acts committed by each side, Ms. Bogner said in an interview. “Our job is to document the facts on the ground. Any serious violation of serious humanitarian law is of high concern.” She said that Ukraine was investigating some of the deaths, but the U.N. was not aware of prosecutions.However, Ukraine’s commissioner for human rights, Dmytro Lubinets, contested the report’s findings about abuses committed by his country’s forces. He said that Ukraine adheres to the Geneva Conventions and asked for “indisputable facts” to back up the report’s allegations.

“Russia has criminally invaded our land, killed and abducted Ukrainian citizens and is still blocking access to our prisoners of war. The magnitude of inhuman treatment and torture is being concealed,” Mr. Lubinets said in a post on the Telegram messaging app.

Ms. Bogner said that conditions of detention in Russian prison camps were shocking. Prisoners reported receiving just enough food to survive, and being denied enough medical care, a practice that they said led to several deaths. In addition, the report documented numerous cases of sexual violence by Russian forces.

The report, covering the period since Russia’s full-scale invasion last February, was assembled by the United Nations High Commissioner for Human Rights and was based on hundreds of interviews.

The investigators did not have full access to prisoners on both sides, so the findings may not be comprehensive. Ukraine allowed the team to conduct interviews with Russian prisoners of war, but Russia did not let investigators talk to Ukrainian prisoners. Interviews with captured Ukrainian soldiers were conducted after their release. Moscow and Kyiv have exchanged hundreds of prisoners in recent months.

In a separate report on human rights, the U.N. said that more than 8,000 civilians had been killed in Russian attacks and nearly 14,000 others had been wounded. Almost all of the victims’ injuries had been caused by explosives rather than bullets. In addition, Russian forces had forcibly abducted and detained hundreds of people, and almost all of those who had since been released had said that they had been tortured.