An unknown man broke a glass showcase in the Hermitage's applied arts hall to steal a 19th-century silver chalice, setting off an alarm.
"The alarm went off, and the Hermitage's security service detained the offender," police said. "The man is being identified at the moment."
The Hermitage, which boasts one of the world's largest fine arts collections, has been at the center of a large-scale theft scandal this year.
The museum announced in late July that 221 items, including icons, medieval and 19th-century jewelry, silverware and enamels, had been stolen from its Russian section. The $4.85 million theft was uncovered during a routine check.
Three people have been charged so far in the probe, which is still going on, including the husband and son of a museum employee, who died last year shortly after the thefts were uncovered.
Several stolen items from the Hermitage collection, including a rare 19th century icon worth $200,000, were recovered in August when they were dropped off anonymously in garbage bins and train station storage lockers.
Inventories of museum collections were ordered nationwide in the wake of the Hermitage heist, and in August it was announced that a famous architect's drawings had disappeared from the state art archives.
