Breaking News: Bomb Blast In Russia Leaves 10 Dead

The unidentified explosive device blew up at 2:20 p.m. on a train that was leaving the Technology Institute station and heading to the Sennaya Square station, Russia's National Anti-Terrorist Committee said. Photos and video from Sennaya Square appeared to show wounded victims on the smoke-filled platform, and a train car with a door blown out.

Frantic commuters reached out through the doors and windows, shouting, "Call an ambulance!"

"People were bleeding, their hair burned," a witness told Russia's Life News. "My girlfriend was in the next car that exploded. She said that he began to shake. When she came out, she saw that people were mutilated."

A wounded victim outside the Sennaya Ploshchad station. (REUTERS/Anton Vaganov)

Meanwhile a sky news report claims one of the blasts came from a device that appeared to be filled with shrapnel.

On the other hand,Putin has said that investigators were looking into all possible causes.

Russia's Fontanka newspaper reported that an unexploded device turned up at a different subway station as crews worked to deactivate it.

St. Petersburg, Russia's second-largest city with more than 5 million residents, is the country's most popular tourist destination. The two stations that were the site of the blast are some of the subway's busiest.

"The causes are not clear, it's too early. We will look at all possible causes, terrorism as well as common crime," Putin responded. "Law enforcement agencies and intelligence services are doing their best to establish the cause and give a full picture of what happened."