Two female suicide bombers killed at least 38 people and injured 38 on two Moscow metro trains in the morning rush hour on Monday, officials said.

Russian civil aviation authorities ordered increased security at airports, fearing further actions.

No group immediately claimed responsibility for the worst attack on the Russian capital for six years.

The first blast tore through the second carriage of a metro train just before 8 a.m. as it stood at the Lubyanka station, close to the headquarters of Russia's main domestic security service FSB. It killed at least 23 people.

About 40 minutes later, another blast in the second carriage of a train waiting at the Park Kultury metro station, opposite Gorky Park, killed 12 to 14 more people, an emergencies ministry spokeswoman said by telephone.

Moscow Mayor Yuri Luzhkov told reporters that female suicide bombers had carried out the attacks. Prosecutors said they had opened a "terrorism investigation" after forensic experts found the remains of a female bomber.

Vladimir Putin cemented his power in 1998 in launching an assault to overthrow a pro-independence government lodged in the Chechen capital Grozny.

Some of the injured were airlifted to emergency hospitals in helicopters. Dozens of commuters were helped from each station to waiting ambulances.

Surveillance camera footage posted on the Internet showed several motionless bodies lying on the floor or slumped against the wall in Lubyanka station lobby and emergency workers crouched over victims, trying to treat them.

"I was moving up on the escalator when I heard a loud bang, a blast. A door near the passage way arched, was ripped out and a cloud of dust came down on the escalator," a man named Alexei told the state-run Rossiya 24 news television channel.

"People started running, panicking, falling on each other," he said.

Russian President Dmitry Medvedev will make a statement to the nation later today, a Kremlin source told Reuters. Prime Minister Vladimir Putin was being updated regularly on developments, local news agencies reported.


Agencies