Two blasts ripped through packed Moscow metro stations during rush hour this morning, killing at least 34 people and wounding 18, Russian officials said.

Russian prosecutors said they suspected "terrorists" were responsible and they had opened an investigation.

No group immediately took responsibility for the blasts but suspicion is likely to fall on groups from Russia's North Caucasus, where Moscow is fighting a growing Islamist insurgency.

The first blast tore through the second carriage of a train as it stood at the Lubyanka metro station, close to the headquarters of Russia's main domestic security service (FSB), killing 22 people.

Another blast wrecked the second carriage of a train waiting at the Park Kultury metro station killing 12 more people, an Emergencies Ministry spokeswoman said.

"The blast hit the second carriage of a metro train that stopped at Lubyanka," ministry spokeswoman Irina Andrianova told Reuters.

She said there were killed both inside the carriage and on the platform. The stations were packed with rush hour commuters.