MOSCOW (Reuters) - Russia's top security official said on Monday that authorities had detained four men from the volatile North Caucasus who were allegedly planning a "large terrorist attack" in or near Moscow.
"Literally several days ago ... a large terrorist attack was averted at the preparation stage in the Moscow area," Federal Security Service director Alexander Bortnikov told President Dmitry Medvedev in televised comments.
Bortnikov said the suspects had planned to target "crowded facilities and transport infrastructure" and that security officers had confiscated homemade bombs, other weapons and a map with a plan for the alleged attack.
Russian authorities frequently claim to have averted attacks by militants based in the North Caucasus, where they are fighting against Islamic insurgents, but claims to have foiled large-scale planned strikes targeting Moscow are more rare.
Insurgent leader Doku Umarov claimed responsibility for a suicide bombing that killed 37 people at Moscow's busiest Domodedovo airport in January and twin bombings on the Moscow metro that killed 40 in March 2010.
Umarov has said he has readied dozens of potential suicide bombers and has threatened more attacks on Russian cities this year. Authorities are nervous about possible attacks ahead of December parliamentary elections and a March presidential vote.
(Reporting by Steve Gutterman; Editing by Alissa de Carbonnel)