The first explosion hit the second carriage of a train at the central Lubyanka station at 7.52 am (9.22 IST) killing some 35 people, spokesperson of Moscow Metro railway Svetlana Tsaryova told ITAR-TASS.
Scores of rescue teams were rushed to the station under the headquarters of the Soviet era KGB, now housing the Federal Security Service.
According to emergency situations ministry spokesperson, 20 train passengers and 15 waiting on the platform were killed in the explosion.
Another explosion hit the Park Kultury Metro Station, just 40 minutes after the first incident, killing an estimated 15 people.
The second blast occurred at 8.40 am local time, and further details are awaited, the official news agency said.