Trevor Reed "voluntarily joined the Ukrainian army as a mercenary on July 25, 2023", Russia's investigative committee said in a statement.

"The court has sentenced him to 14 years and six months," it said.

Reed was a Texas university student in 2019 when he travelled to Russia with his Russian girlfriend.

He was arrested for assaulting law enforcement officers after getting drunk, and was sentenced to nine years in prison.

He was released in April 2022 after the White House negotiated an exchange for Konstantin Yaroshenko, a Russian pilot and drug smuggler sentenced to 20 years in prison by an American court.

On July 26, 2023, the US State Department said Reed had been wounded during fighting in Ukraine.

Russia's Investigative Committee said he had been fighting in the Donetsk region in eastern Ukraine.

On Monday, a Russian court sentenced a 72-year-old US citizen accused of fighting as a mercenary on the side of Ukraine to nearly seven years in prison.

Stephen Hubbard had been in custody for more than two years and was sentenced after a trial held behind closed doors.

Several Westerners, including Americans, are currently imprisoned in Russia.

Among them is Ksenia Karelina, a US-Russian national sentenced to 12 years in prison in August for donating around $50 to a Ukrainian organisation.

Washington accuses Moscow of imprisoning US nationals to ensure the liberation of Russian agents held abroad in prisoner exchanges.

Russia and the West carried out the biggest such swap since the Cold War on August 1 of this year.

It saw the freeing of US reporter Evan Gershkovich as well as several Russian opposition figures in exchange for Russian agents, including a killer convicted in Germany.