Four Russian soldiers have been charged with war crimes for allegedly abducting and torturing a US citizen living in Ukraine, officials said.

US prosecutors say the American national had been living in Ukraine since 2021 and had not fought or participated in the war.

He was held for around 10 days in April 2022, and was allegedly subjected to mock executions and beatings.

This is the first time the US has filed charges under its war crimes law.

Two of the men charged were named as commanding officers Suren Seiranovich Mkrtchyan and Dmitry Budnik. The other two were lower-ranking soldiers named as Valerii and Nazar, but their surnames are unknown, according to court documents.

Announcing the charges on Wednesday morning, Attorney General Merrick Garland said this was "an important step towards accountability for the Russian regime's illegal war in Ukraine".

"Our work is far from done," he said, noting that the Department of Justice spent decades investigating Nazi war criminals who had resettled in the US.

"The Justice Department - and the American people - have a long memory," Mr Garland said. "We will not forget the atrocities in Ukraine. And we will never stop working to bring those responsible to justice."

The four soldiers are still at large, and the US has no extradition treaty with Russia, making the charges somewhat symbolic. However, Russians facing criminal charges in the US have previously been taken into custody when they travelled overseas.

The alleged crimes took place after Russian forces captured the small village of Mylove, on the Dnipro River in south-east Ukraine.

The American civilian was abducted from his home by the soldiers, prosecutors said, and was thrown to the ground naked with his hands tied behind his back.

He was then taken to a makeshift jail in the village, where he was tortured and threatened with sexual assault and execution, according to court documents.

The indictment unveiled on Wednesday included detailed descriptions of interrogation and torture, and prosecutors said that at several points the soldiers told the American civilian that he was about to die.

During one mock execution, Nazar and others allegedly forced the man to the ground, put a gun to the back of his head, then moved the gun slightly and shot a bullet just past the man's head.

The victim was allegedly also forced to perform manual labour such as digging trenches for the Russian troops. After around 10 days he was released.

The US war crimes law, passed in 1996, criminalised any "grave breach" of the Geneva Conventions involving Americans as victims or perpetrators.

The charges against the Russian soldiers include conspiracy to commit war crimes, torture, inhuman treatment, and unlawful confinement. If caught, tried and convicted, they face a maximum sentence of life in prison.

The BBC has contacted the Russian Foreign Ministry for comment.