Viktor Bout, a freed Russian arms dealer, joins an ultranationalist group.

According to the party's chairman, a Kremlin supporter, Russian arms dealer Viktor Bout, who was released from US imprisonment last week in exchange for American basketball player Brittney Griner, has joined the ultranationalist Liberal Democratic Party (LDPR).

LDPR head Leonid Slutsky said on Telegram on Monday that Bout had received "the party card of the Liberal Democratic Party directly presented" to him.

"I have no doubt that Viktor Bout, a courageous and independent individual, will occupy a deserving position in it." He wrote in a post with a picture of the two men, "Welcome to our ranks!"

The LDPR, a hardline, ultranationalist organization founded in 1991, calls for Russia to retake the nations that made up the former Soviet Union.

It has been one of the most ardent proponents of the invasion of Ukraine, frequently urging Moscow to take tougher action.

The party now plays a minor role in Russian politics, but it nonetheless opposes the United Russia coalition that is currently in power in a symbolic way while remaining mostly in line with Kremlin policy.

Griner, who was detained in mid-February after officials at the Moscow airport discovered cartridges carrying cannabis oil in her luggage, was exchanged for Bout, who was released from a 25-year prison sentence on December 8 and returned to Russia.

Griner, who according to the US State Department was "wrongfully imprisoned," received a nine-year prison term in August.

Bout had been detained by US officials in Thailand in 2008, and prosecutors had accused him of providing material support for "terrorism" through his massive arms trafficking in high-risk areas around the globe. The arrest, according to the Kremlin, was made for political reasons.

In addition to being referred to as the "dealer of death," Bout has been accused of breaking UN arms embargoes in Angola, Sierra Leone, Liberia, and the Democratic Republic of the Congo.

The prisoner exchange took place nine months after Russia invaded the neighboring Ukraine, a conflict that soured relations between Washington and Moscow further and made it more difficult to negotiate releases.

Bout's release was celebrated in Russia as a win for Moscow.

The US government of US President Joe Biden was criticized for approving the trade, with critics pointing to the contrast in the seriousness of the allegations leveled against Bout and Griner.

The fact that Paul Whelan, a former marine serving a 16-year sentence for alleged espionage in Russia, was not freed as part of the deal particularly incensed Biden's detractors.

Vladimir Zhirinovsky, the LDPR's founder and longtime leader, gained a reputation as a political showman for his spectacular pranks and eccentric behaviour before his death in April. The LDPR has a history of enlisting controversial figures into Russian politics.

Andrey Lugovoy, a former KGB agent who was wanted in Britain for the death of former Russian spy Alexander Litvinenko the year before, was chosen to represent the LDPR in parliament in 2007.

In his first interview upon his release, Bout said that the West had attempted to "destroy and split" Russia in the years following the fall of the Soviet Union. Bout spoke to the state-run Russia Today station