Dozens of Westerners, including Americans, have been imprisoned in Russia, especially after the start of the Ukraine war in 2022, with many of them later swapped in prisoner exchanges.

"A US citizen was found guilty of illegally transporting and moving firearms," the regional courts' press service said in a statement.

It identified the man as Charles Wayne Zimmerman, and said he "admitted his guilt in full" and was "sentenced to five years in prison".

It did not mention when exactly the man was sentenced but said an appeal against the conviction had been rejected.

It was the first time his arrest and conviction has been mentioned in Russian media, which usually covers judicial proceedings of foreign citizens closely.

According to the court, the man sailed across the Atlantic Ocean and the Mediterranean Sea.

It cited him as saying that he had met a Russian woman online and decided to visit her, and that he did not know he was forbidden to keep a weapon on board his yacht while it was docked in Russia.

In September 2024, the US Coast Guard East issued a missing person alert for a man identified as Charles Zimmerman, 57, who departed on a sailing trip from Fort Macon, North Carolina, to New Zealand.

"Zimmerman was last heard from on July 23 (2024). He had informed a family member that he would be departing in his sailing vessel en route to the Mediterranean Sea," the Coast Guard said on Facebook.

He was sailing on a 35-foot (10-metre) green and white-hulled vessel, named the Trude Zena, it added.

Announcing Zimmerman's sentence, the Russian court published on social media a slideshow which included a video of a white sailing boat, photos of a sniper rifle and ammunition allegedly found on board, and of a man sitting on the vessel.

Washington accuses Moscow of imprisoning US nationals in a bid to swap them for Russian spies held abroad.