Eight people have been arrested in connection with four apartment bombings in September that killed 300 people, federal officials said today.
Vladimir Kozlov, a Federal Security Service official, said Russia had launched an international search for nine other suspects in the bombings.
Kozlov said the three men believed to have masterminded the bombings are hiding in the breakaway republic of Chechnya, though he did not say if they were Chechen.
Russia has said that people connected to militants from Chechnya were responsible for the bombings, which devastated two apartment buildings in Moscow and one each in the southern cities of Buinaksk and Volgodonsk.
The blasts, along with two invasions by militants into the region of Dagestan this summer, were the main pretext for the government's military operation to retake control of Chechnya.
Police have previously reported charging one man in connection with the bombings and arresting several more. It wasn't immediately clear today whether those were among the group of eight.