ST. PETERSBURG (Reuters) -- A car exploded in Russia's second city, St. Petersburg, killing three people and seriously injuring a fourth, the Emergency Situations Ministry said.
"At 8:55 [0555 GMT] a car containing a grenade exploded. Three people were killed, including a child aged between 2 1/2 and 3 years old," ministry spokesman Andrei Alyabev said.
Russian news agencies quoted the chief of St. Petersburg's city police force as saying the explosion was not an act of terrorism.
Russian state television channel Vesti-24 said investigators are treating the blast as murder.
The dead were members of the same family and the seriously injured man was a taxi driver, Russian news agencies reported. The driver is in hospital in a serious condition, they said.
The explosion took place around 50 meters from the city's Udelnaya metro station during morning rush hour. The station was not closed after the explosion, Alyabev said.