The soldier -- whose name was not released -- adds to the number of Americans held in Russia at a time of deep tensions with Washington over Moscow's invasion of Ukraine.

"On May 2, 2024, Russian authorities in Vladivostok, Russia, detained an American soldier on charges of criminal misconduct," US Army spokeswoman Cynthia Smith said.

Russia notified the US State Department, which is "providing appropriate consular support to the soldier in Russia," and the Army notified his family, Smith said.

"Given the sensitivity of this matter, we are unable to provide additional details at this time," she added.

When asked earlier about reports of a soldier's detention in Russia, US National Security Council spokesman John Kirby said: "We are aware of this case."

NBC News said the soldier traveled to Russia on his own and was not on official business.

The soldier, a staff sergeant, was arrested on suspicion of theft and was being held in pre-trial detention, CNN reported.

- Other Americans held abroad -

It is the second time in less than a year that a US soldier has been detained after entering a country with which the United States has strained ties.

Travis King crossed the border into North Korea last July and was held there until being expelled in September. He was later charged with desertion.

Russian authorities have arrested several US citizens in recent years, with critics accusing Moscow of using detainees as bargaining chips to exchange for Russians jailed in the United States.

In December 2022, Russia released American basketball superstar Brittney Griner in exchange for notorious Russian arms dealer Viktor Bout -- known as the "Merchant of Death."

There are ongoing efforts to free other Americans who remain in Russian detention.

Paul Whelan, a former US Marine, was sentenced in 2020 to 16 years in jail on spying charges that he denies.

In late March 2023, Wall Street Journal reporter Evan Gershkovich, 32, became the first Western journalist to be held on espionage charges in Russia since the Soviet era.

He, his employer and the US government all reject those charges.

A US-Russian dual citizen, journalist Alsu Kurmasheva, was arrested in October. She has been charged with failing to register as a "foreign agent" as required by the authorities.