MOSCOW (Reuters) - Gordon Black, a U.S. soldier being held in the Russian city of Vladivostok, has pleaded guilty to theft charges and is cooperating with investigators, Russia's RIA state news agencies reported on Thursday.

"He is cooperating (with the investigation), he admitted (guilt)," RIA cited a representative of the local interior ministry as saying.

Black could not be reached for comment by Reuters.

Black, a U.S. staff sergeant, was detained on May 2 by police in the Russian Far Eastern city of Vladivostok on suspicion of stealing from a woman he was in a relationship with. The court ordered he remains detained until July 2.

The United States warns its citizens against all travel to Russia, citing an array of reasons, including "the potential for harassment and the singling out of U.S. citizens for detention by Russian government security officials" and the arbitrary enforcement of the law.

A handful of U.S. citizens have been detained since Russia launched its invasion on Ukraine in February 2022, including Evan Gershkovich, a Wall Street Journal reporter, who was detained in 2023 on charges of spying.

(Reporting by Moscow; Writing by Lidia Kelly in Melbourne; editing by Guy Faulconbridge)