Dhaka, Nov. 29 -- When a dozen Russian soldiers stormed into Dmytro Bilyi's home in August, the 24-year-old police officer said they gave him a chilling choice: Hand in his pistol or his mother and brother would disappear.

Bilyi turned his gun over to the soldiers, who carried machine guns and had their faces concealed. But it didn't matter. They dragged him from his house in Ukraine's southern village of Chornobaivka to a prison in the nearby regional capital of Kherson, where he said he was locked in a cell and tortured for days, his genitals and ears shocked with electricity.

"It was like hell all over my body," Bilyi recalled. "It burns so bad it's like the blood is boiling ... I just wanted it to stop," he said.

More than two week...