Eighteen-year-old orphan Denys Kostev is one of 4,000 Ukrainian children who Kyiv says were unlawfully taken to Russia following the invasion of Ukraine in February 2022.

Russia says it only moved the children to protect them from war.

Reuters investigated the fates of Kostev and more than 50 other orphans who were taken from the Ukrainian city of Kherson.

Kostev emerged as a regular participant in pro-Russian videos filmed and shared widely online. 

Some see him as a collaborator and propagandist.

The teenager, who fled Russia in February and is now living in Poland, told Reuters he took part in the videos because he felt threatened.

"They just asked and I did it. There is a war going on and you don't know how to live, how to survive. You're alone. There's no one around you who is worried about your life. Nobody needs you. And when your life is threatened, you will do anything to keep yourself safe.'"

Reuters was unable to verify Kostev's account of being pressured by officials loyal to Moscow.  

But three orphans who lived with him in Russian-occupied territory have described similar experiences.

The Kremlin and Russia's children's rights commissioner, Maria Lvova-Belova, did not respond to requests for comment.

In March 2023, the International Criminal Court issued arrest warrants for Lvova-Belova and her boss, Russian President Vladimir Putin, on charges of illegally deporting children from Ukraine.

Russia denounced the warrants as "outrageous and unacceptable."

After being taken away from his orphanage in Kherson in the fall of 2022, Kostev ended up in Henichesk, a city in Russian-occupied territory in the Kherson region.

Kostev says he and other orphan teens were lodged in cold, damp dormitories of a local school.

"We were shocked. I took a video of the conditions of where we were sent to. In my room, when I came in, it was zero degrees Celsius. I'd walk in, breathe on a light bulb, and I'd have steam coming out of my mouth."

"After I recorded these videos of the living conditions, that was it, I was an enemy of the people there. The next day the police were called and they gave me a verbal warning, they said, 'If you kick up a big fuss, it won't be very good for your life.'"

(Journalist) "What does 'won't be very good' mean exactly?"

"Well, to be direct, they literally threatened me and said, 'We'll take you to the forest and, to put it mildly, just give you a good beating.'"

Kostev says he was also instructed to take part in video interviews. In one, filmed by Russia's state-controlled RT TV channel, Kostev praises the Russian army.

He says the TV journalists gave him a script beforehand and told him to repeat it on camera.  

RT did not respond to requests for comment.

Kyiv says many taken Ukrainian orphans have been subjected to an orchestrated program to make them accept Kremlin ideology.

Moscow denies this.

By summer 2023, Kostev left Henichesk and moved to Russia.

But by the end of the year, he had re-established contact with his half-brother who lives in Germany, and began talking about moving there.

"I missed my family very much. I thought a lot about my family. I mean, I'd been an orphan my whole life. And an opportunity came up to leave. I wanted to go back to my family. And I said I'm going back to my family any way I can."

Kostev left Russia in February. Russian officials did not try to stop him.

He is now living in Poland and waiting for paperwork so he can enter Germany.

He says he wants stay out of politics and get on with his life.

"You realize that you are entering a new stage of your life, you can build everything from scratch again, it's all in your hands. Everyone gets tired of moving around the world. I'm a little tired, and I want to stop living a nomadic life. I want to stay in one place and live in peace."