Hubbard, 72, is serving almost seven years in prison for allegedly fighting as a mercenary with Ukraine's army
Hubbard, 72, is serving almost seven years in prison for allegedly fighting as a mercenary with Ukraine's army AFP

US-Russian citizen Ksenia Karelina was on a plane back to the United States on Thursday after being released in a prisoner exchange between Moscow and Washington, her lawyer and America's top diplomat said.

She spent more than a year in Russian prison after being charged with "treason" for donating to a pro-Ukrainian charity.

The prisoner swap was the second between Moscow and Washington since US President Donald Trump took office.

Here are some of the most high-profile instances of US citizens still in Russian prisons:

Stephen Hubbard, in his early 70s, is serving almost seven years in prison after a Russian court convicted him of fighting as a mercenary with Ukraine's army.

Originally from Michigan, Hubbard was a retired English teacher living in the Ukrainian town of Izyum, in northeastern Ukraine, when Russia launched its February 2022 offensive.

He was captured shortly after and held incommunicado for two and a half years before being put on trial in Moscow in October, accused of being paid to fight with a Ukrainian territorial defence battalion.

A Ukrainian soldier detained with Hubbard told AFP last year that the American was beaten with sticks and truncheons, forced to simulate sexual acts with other prisoners and starved while in captivity.

American soldier Gordon Black was jailed in June 2024 for three years and nine months by a court in the far eastern city of V

ladivostok, convicted of having threatened to kill his girlfriend and for stealing from her.

A Russian court reduced his sentence to three years and two months on Monday.

The then 34-year-old, who completed tours in Afghanistan and Iraq, was visiting a Russian woman he had met and dated while serving in South Korea.

US media have said the arrest could have been a "honey trap" operation targeting an American citizen.

Former US marine Robert Gilman from Massachusetts is serving seven years after being convicted of having attacked Russian police officers and prison guards.

Originally convicted in 2022 of attacking a police officer while drunk, he was handed the longer term last year after prison authorities said he punched staff and attacked a criminal investigator.

His backers say the charges are unsubstantiated and that he has been subjected to "forced drugging" and "torture" in prison.

A former US paratrooper, Michael Travis Leake, was detained in June 2023 and sentenced to 13 years in prison for selling illegal

narcotics.

CNN reported that Leake, who fronted a Moscow-based rock band called Lovi Noch, had lived in Russia for many years.

Joseph Tater faces five years in prison on accusations of assaulting a police officer after a confrontation with staff at a Moscow hotel.

In a court hearing last year he rejected his US citizenship and claimed he had been targeted by the CIA for years.

Russian state media reported last week that he had been forcibly hospitalised, after a board of Russian doctors accused him of impulsiveness and having "delusional ideas".

Russian-born Gene Spector was sentenced to 15 years on espionage charges in December.

No details of the accusation against him have been released.

Spector, born in Leningrad -- now Saint Petersburg -- in 1972 was already serving a jail sentence on bribery charges when convicted of espionage.

US-Russian citizen Ksenia Karelina is serving 12 years for donating around $50 to a pro-Ukraine charity
US-Russian citizen Ksenia Karelina is serving 12 years for donating around $50 to a pro-Ukraine charity AFP
US media have suggested Black could have been the victim of a 'honey trap' operation
US media have suggested Black could have been the victim of a 'honey trap' operation AFP
Joseph Tater faces five years' prison over allegations of assaulting a police officer
Joseph Tater faces five years' prison over allegations of assaulting a police officer AFP
Former US paratrooper Michael Travis Leake was detained in June 2023
Former US paratrooper Michael Travis Leake was detained in June 2023 AFP