Russian arms dealer Viktor Bout, freed from a US jail last year, on Friday urged US ex-president Donald Trump to seek refuge in Russia as his life was "in peril".

Bout, also known as the "Merchant of Death", was swapped for US basketball star Britney Griner in a high-profile prisoner exchange between Moscow and Washington in December.

"I believe your life is in peril," Bout wrote in a telegram sent to Trump and shown to the press in Moscow.

"The Biden administration will not stop just by dragging you through the court/prison industrial complex," he said, referring to Trump's successor Joe Biden.

"They would sooner end your life than let you stand in their way."

Bout told Trump, whom he has long admired, that he would find a "safe haven and from here you can lead the fight for the American people."

Bout was serving a 25-year sentence in a US prison when he was swapped for Griner. He has since joined a Russian nationalist party.

Accused of arming rebels in some of the world's bloodiest conflicts, Bout was arrested in Thailand in a US sting operation in 2008, extradited to the United States and sentenced in 2012.

Washington and Moscow have in recent years held several prisoner exchanges.

There are still several Americans held in Russia.

Last week, Russia arrested US journalist Evan Gershkovich and charged him with espionage, provoking an international outcry.

Washington has called the charges against him "ridiculous."