Dozens of people were killed and more than 25 injured when two female suicide bombers blew themselves up on subway trains during the morning rush-hour in Moscow, Russian officials said.
Emergency Ministry spokeswoman Veronika Smolskaya said 22 people were killed in the first blast, at Lubyanka station in central Moscow. The station is underneath the building which houses the main offices of the Federal Security Service, the KGB's main successor agency.
A second explosion hit Park Kultury station about 45 minutes later. Ms Smolskaya said at least 12 were killed there.
The last confirmed terrorist attack in the Russian capital was in August 2004, when a suicide bomber blew herself up outside a city subway station, killing 10 people.
Responsibility for that blast was claimed by Chechen rebels, and suspicion in today's explosions is likely to focus on them and other separatist groups in the restive North Caucasus region.
Moscow's subway system is one of the world's busiest, carrying around seven million passengers on an average workday, and is a key element in running the sprawling and traffic-choked city.
The blasts practically paralysed movement in the city centre as emergency vehicles sped to the stations. Helicopters hovered over the Park Kultury station area, which is near the renowned Gorky Park.
Passengers, many of them in tears, streamed out of the station, one man exclaiming over and over "This is how we live!"
At least a dozen ambulances were on the scene.