A Dagestani allegedly linked to rebels was arrested in Moscow, Interfax reported Monday.
The detained man, 39, had two guns, former pneumatic weapons rigged with silencers and modified to shoot real bullets, as well as four full magazines, the report said, citing police. It did not disclose his identity.
A criminal case was opened for illegal arms trafficking, which carries a maximum punishment of three years in prison.
Authorities are looking into the man's alleged links to the North Caucasus rebels.
"There is certain information that the detainee could be linked to a series of murders of people who helped law enforcement officials find rebels," the statement said.