Ten people said to be preparing terrorist attacks in Moscow and St Petersburg and who had contacts with Islamic State have been arrested, Russia's security service said.
The statement from the Federal Security Service was reported by Russian news agencies on Saturday.
The security service, known by its acronym FSB, said those arrested were from Central Asian countries.
It did not specify the countries but said the arrests were made in cooperation with the former Soviet republics of Kyrgyzstan and Tajikistan.
The FSB said homemade bombs and firearms were seized and the suspects admitted to having contact with Islamic State.