A US man who was imprisoned by Russia for almost three years prior to being released in a 2022 prisoner swap has been injured while fighting in Ukraine.

Ex-US Marine Trevor Reed was hurt while fighting against Russia's invasion, the US State Department said on Tuesday.

Officials add that he "was not engaged in any activities on behalf of the US government" and reiterated that Americans should not travel to Ukraine.

Mr. Reed has been transported to Germany by a non-governmental organization.

State Department deputy spokesperson Vedant Patel said at a briefing that US officials "are aware" of Mr. Reed's injuries and the fact that he has been taken to Germany for treatment.

"We have been incredibly clear that traveling to Ukraine, choosing to participate in the fighting there, has a very real risk of capture, of death, of bodily harm, and that continues to be our assessment," Mr Patel said.

The circumstances of Mr. Reed's injuries - and how or when he came to fight for Ukraine - are not clear. Officials tell US media he was injured in eastern Ukraine before being taken to a hospital in Kyiv and then sent on to Germany.

The Messenger, which first reported Mr. Reed's injuries, says he suffered shrapnel wounds from stepping on a land mine two weeks ago.

According to CBS News, the BBC's US partner, sources say he is being treated at a military faculty in the German town of Landstuhl for a laceration to an extremity.

In 2019, Mr. Reed was convicted in Russia of fighting with police officers while on a drunken night out.

The US had deemed him to be wrongfully detained in Russia, calling his trial "theatre of the absurd".

He was released in 2022 in exchange for a Russian pilot who had been convicted in the US of cocaine smuggling charges.

The US is currently working to free two Americans also considered to be wrongfully detained in Russia - businessman Paul Whelan and journalist Evan Gershkovich.

Russia and Ukraine have not yet commented on Mr Reed's injuries.

David Whelan, a brother of Paul Whelan, said in a statement: "I'm sorry to hear that he's been injured. But a hostage's release isn't an endpoint.

"They have to live with the aftermath after the hostage takers and others move on. I can't imagine the anger, vengeance, and grief they must feel.

"I hope he finds some peace now."

Sorry to him.