Russian authorities have detained 140 people suspected of ties to Islamic extremism at a mosque in Moscow.
Russian state media quoted a Russian Federal Security Service statement as saying those detained Friday included more than 30 citizens of other countries. But the statement did not specify which nations.
The detentions reportedly involve people suspected of involvement with extremist groups. Russia's Interfax news agency says the operation was aimed at identifying people wanted for terrorist and extremist crimes.
Interfax reports the FSB statement said law enforcement officials believe the prayer house in southern Moscow where the detentions occurred was often visited by people who later converted to radicalism, joined militant groups in the North Caucasus and participated in terrorist acts in Russia.
Media reports did not say whether any charges have been filed.
The detentions come after two ethnically Chechen brothers were identified by U.S. authorities as suspects in the deadly April 15 Boston Marathon bombings.
Russian President Vladimir Putin has used the bombings in Boston as an opportunity to call for greater cooperation with the United States in fighting terrorism.
He said Thursday the attack proved that his policy on the restive North Caucasus region was correct and the West was wrong, as he put it, in supporting the militants in Chechnya.
The U.S. had urged the Kremlin to seek a political settlement in Chechnya and provided humanitarian aid to the region during the separatist war that began there in 1994.
Some information for this report was provided by AP.