Russia's state investigative committee saidtoday that the deadly St Petersburg metro blast was caused by a bomb that had possibly been detonated by a man whose body parts were found in one of the train carriages.

"It has been ascertained that an explosive device could have been detonated by a man, fragments of whose body were found in the third carriage of the train," the committee, which has sweeping powers, said in a statement.

"The man has been identified but his identity will not be disclosed for now in the interests of the investigation," the statement added.

Earlier, officials said the likely suspect was a Kyrgyz-born Russian citizen.

The bomb killed 11 people and wounded about 40 others on a train.

Hours later, the police found and defused a shrapnel-packed explosive device at another St Petersburg station.

There was no immediate claim of responsibility for the attack, which came while President Vladimir Putin was visiting the city, his hometown.

In the past two decades, Russian trains and planes have been frequent targets of terrorism, usually blamed on Islamic militants.
 
The Investigative Committee, the country's top criminal investigation body, said it had begun a probe based on the assumption that it was terrorism but added that other possibilities were being considered.

President Putin lays flowers on the site of the explosion.

St Petersburg, a major tourist destination famed for its imperial palaces and lavish art museums, had been spared previous attacks.

"From now on, I will be scared to take the subway," said Marina Ilyina, 30, who brought flowers to the station where the train stopped after the bombing. "We in St. Petersburg thought we wouldn't be touched by that."

The explosion occurred in mid-afternoon as the train travelled between stations one of the city's north-south lines.

The driver chose to continue on to the next stop, Technological Institute, a decision praised by the Investigative Committee as aiding evacuation efforts and reducing the danger to passengers who would have had to walk along the electrified tracks.