Ten people have been arrested for allegedly serving as agents of the Russian government in the United States, the US justice department has said.
Eight of the 10 were arrested on Sunday for allegedly carrying out "long-term, deep cover assignments" in the US on behalf of Russia.
Two others were arrested for allegedly participating in the same Russian intelligence programme within the United States.
Their job, according to the court papers in the case, was "to search and develop ties in policymaking circles" in the United States.
The suspects were arrested in the US states of New York, Virginia, New Jersey and Massachusetts.
FBI officials described the arrests as the result of a "multi-year" investigation.
Each of the 10 was charged with conspiracy to act as an agent of a foreign government, which carries a maximum penalty of five years in prison.
The cases were filed in the US district court for the southern district of New York.
The Russian government has not commented on the arrests.