Hundreds of Ukrainians, including civilians and local politicians, are being subjected to forced detentions by Russian forces in occupied regions, the UN has told the BBC.
Officials said they had verified some 271 cases of forced detentions, with many of those seized facing torture.
Separately, a Ukrainian politician told the BBC that he was waterboarded after being abducted by the Russian military.
Russia’s defence ministry did not reply to a request for comment on the claims.
Oleh Pylypenko, the elected head of the Shevchenkivska united territorial community in southern Ukraine, said he was seized by Russian paratroopers near Kherson on 10 March while delivering aid to constituents.
The 36-year-old told the BBC that he was arrested along with his driver at a roadblock by Russian troops and suspected he was deliberately targeted after sharing the locations of Russian artillery with Ukrainian forces.
“I think that they started hunting specifically for me almost from the very start of the war. I believe they were planning an ambush because they wanted to take me alive,” he said.
He was subsequently taken to an airfield, where allegedly he was tortured for three days by Russian paratroopers.
“They didn’t touch my driver,” Mr Pylypenko recalled. “They were interrogating only me. They used physical violence, electric currents and poured cold water over me during freezing temperatures outside. I had frostbite on my feet, damaged ribs and internal organs.”
The father of three added that paratroopers also beat him with a “rubber club” and kicked him until he passed out. He also alleged that he was repeatedly subjected to electric shocks by the Russian troops.
“On the third day of all this I was so badly beaten up that I unable to move [independently]. And I wouldn’t have survived without my driver, who was helping me all the time,” he said.