The U.N. human rights office (OHCHR) said on Tuesday that both Russia and Ukraine have tortured prisoners of war during the nearly nine-month conflict, citing examples including the use of electric shocks and forced nudity.

The U.N.’s Ukraine-based monitoring team based its findings on interviews with more than 100 prisoners of war on each side of the conflict since April. The interviews with Ukrainian prisoners of war were conducted after their release, since Russia did not grant access to detention sites, it said.

Matilda Bogner, head of the monitoring mission, told a Geneva press briefing that the “vast majority” of Ukrainian prisoners they interviewed held by Russian forces reported torture and ill-treatment. She gave examples of dog attacks, mock executions, electric shocks with Tasers and military phones and sexual violence.

Bogner, who is one of the U.N. interviewers and spoke to journalists via videolink from Ukraine, said the treatment was aimed at intimidating and humiliating them. One man in a penal colony near Olenivka told the team that members of Russian-affiliated armed groups “attached wires to my genitalia and nose and shocked me. They simply had fun and were not interested in my replies to their questions.”

Russia’s defence ministry did not immediately respond to an emailed request for comment. Russia, which invaded Ukraine on Feb. 24, denies torture or other forms of maltreatment of POWs.

On the Ukrainian side, Bogner reported “credible allegations” of summary executions of Russian prisoners, noting that no progress has yet been seen in Ukrainian authorities’ investigations into these cases.