Female suicide bombers struck today in two central Moscow subway stations, killing at least three dozen people in the latest attack by Chechnyan Muslim fanatics: Toll From Moscow Bombing at 37.

MOSCOW — Female suicide bombers set off huge explosions in two subway stations in central Moscow during the Monday morning rush hour, Russian officials said, killing more than three dozen people and raising fears that the Muslim insurgency in southern Russia was once again being brought to the country’s heart.

The first attack occurred as commuters were exiting a packed train at a station near the headquarters of the F.S.B., the successor to the Soviet-era K.G.B. Officials said they suspected that the attack there was intended as a message to the security services, which have helped lead the crackdown on Islamic extremism in Chechnya and other parts of the Caucasus region in southern Russia.

The two explosions spread panic throughout the capital as people searched for missing relatives and friends, and the authorities tried to determine whether more attacks were planned. The subway system is one of the world’s most extensive and well-managed, and it serves as a vital artery for Moscow’s commuters, carrying as many as 10 million people a day.

“The terrorist acts were carried out by two female terrorist bombers,” said Moscow’s mayor, Yuri M. Luzhkov. “They happened at a time when there would be the maximum number of victims.”