- Dmitry Medvedev warned freed Russian dissidents to watch their backs after the recent prisoner exchange.
- Prisoners swapped in the deal with the West included Vladimir Kara-Murza and Ilya Yashin.
Russian opposition figures and dissidents freed in Thursday's mass prisoner exchange should "adopt new names" and "disguise themselves," a senior Russian politician has said.
Dmitry Medvedev, Deputy Chairman of Russia's Security Council and a former Russian president, made the thinly veiled threat in a post on Telegram on Thursday.
"I would like, of course, for Russia's traitors to rot in a penitentiary or die in prison, as has often happened. But it is more useful to get out our own people, who worked for the country, for the Fatherland, for all of us," he wrote.
"Let the traitors now feverishly adopt new names and actively disguise themselves under the witness protection program," he added.
In a follow-up post on Sunday, Medvedev said: "Let them keep on barking, dreaming of tearing apart the body of our country."
"Let them not forget about the perishability of their existence in this world. Let them burn in hell!" he said.
Among those released by Russia were Vladimir Kara-Murza, a Pulitzer Prize-winning writer who was serving 25 years on a treason conviction; opposition activist Ilya Yashin, imprisoned for his criticism of the war in Ukraine; and Oleg Orlov, a human rights campaigner.
Russia has a history of attempting to take out critics and defectors.
As Russian President in 2010, Medvedev pardoned jailed British double agent Sergei Skripal.
Eight years later, a Russian hit squad traveled to Salisbury, England, and poisoned him and his daughter with a Novichok nerve agent.
Despite falling critically ill, both survived the incident.
In 2006, Russian defector Alexander Litvinenko died in a London hospital, killed by highly toxic radioactive polonium 210, which is thought to have been administered in a cup of tea.
Litvinenko had worked as an officer in Russia's Federal Security Service (FSB), but he fled to the UK and began criticizing the Kremlin.
On Sunday, Medvedev also welcomed the return of agents who had been jailed in the West, including Vadim Krasikov, a Russian hitman.
"There is no doubt that the returned citizens are patriots of our Fatherland, who have accomplished great feats," he wrote on Telegram.