Russia's Foreign Ministry says it is studying US statements about the arrest of 10 alleged Russian spies. Ministry spokesman Igor Lyakin-Frolov says the information given by US authorities looks "contradictory." He wouldn't comment further.
The main Russian spy agency, the Foreign Intelligence Service, refused to comment on Tuesday.
The series of arrests of purported deep cover agents followed a multiyear FBI investigation.
The FBI has arrested 10 people who allegedly spied for Russia for up to a decade posing as innocent civilians while trying to infiltrate US policymaking circles and learn about US weapons, diplomatic strategy and politics. An 11th defendant a man accused of delivering money to the agents remains at large.