Former US marine Trevor Reed has described his experience in a Russian psychiatric facility in a television interview, detailing how he and severely mentally ill inmates were kept in squalid conditions.
Mr Reed, detained in Moscow in 2019, was freed on April 28 in a prisoner swap that took place amid the most tense US-Russia bilateral relations in decades over the war in Ukraine.
In excerpts from an interview with CNN, Mr Reed said he was held with seven other prisoners in a cell at a psychiatric treatment facility.
The Russian embassy in Washington had no immediate comment on Mr Reed's remarks.
Most of the inmates were in there after committing violent crimes including murder and were “just really disturbed individuals”, he said and added that he feared for his life.
“Inside of that cell, you know, that was not a good place,” Mr Reed said.
“There was blood all over the walls there — where prisoners had killed themselves or killed other prisoners or attempted to do that.
“The toilet's just a hole in the floor. And there's, you know, [excrement] everywhere, all over the floor, on the walls. There's people in there also that walk around that look like zombies.”
He told CNN he believed he was put in the facility because of his continued push to appeal his conviction.
Mr Reed was convicted in 2019 of endangering the lives of two police officers after becoming intoxicated on a visit to Moscow.
The US government called the charges political theatre.
The former marine said he did not allow himself to believe he was ever getting out.
“I wouldn't let myself hope,” he said.
Following Russia's invasion of Ukraine on February 24, relations between Moscow and Washington have been at their worst since the Cold War.
Former marine Paul Whelan and basketball star Brittney Griner, a two-time Olympic gold medallist, remain detained in Russia.
Mr Whelan's family has been calling on the Biden administration to press his case with Moscow, especially after Mr Reed's release in exchange for Russian pilot Konstantin Yaroshenko.
“Apparently we need to do more because not everyone is on board with securing Paul's release,” Mr Whelan's brother, David Whelan, said in a statement on Thursday.