There was no immediate claim of responsibility in the bombings, which came in quick succession — a common tactic employed by Kashmiri militants. The blasts came hours after a series of grenade attacks by Islamic extremists killed eight people in the main city of India's part of Kashmir.
India's major cities were put on high alert. Prime Minister Manmohan Singh convened an emergency Cabinet meeting and said that "terrorists" were behind the attacks, which he called "shocking and cowardly attempts to spread a feeling of fear and terror among our citizens."
Pakistan, India's rival over the disputed territory of Kashmir, quickly condemned the bombings.
In Washington, Secretary of State Condoleezza Rice said the U.S. condemns "this terrible terrorist incident. ... It simply shows that this kind of hideous incident can happen anywhere in the world against innocent people."
The U.S. State Department said it had no information about whether there were any American casualties.
Commuter transit systems have been tempting targets for terrorists in recent years, with bombers killing 191 in Madrid, Spain, in 2004, and 52 in London last year.
Chaos engulfed the crowded rail network in India's financial capital following the blasts that ripped apart densely packed carriages on trains that police said had either pulled into stations or were traveling between them. Doors and windows were blown off the train cars, and witnesses said body parts were strewn on the ground.
After meeting with his Cabinet, Maharashtra state Chief Minister Vilasrao Deshmukh said Tuesday night that the death toll was 147, with another 439 wounded.
Deshmukh, the state's top elected official, also corrected initial reports of seven blasts, saying there had actually been eight, including two at one station.
Authorities struggled to treat survivors and recover the dead into the night. Survivors clutched bandages to their heads and faces, and some frantically dialed their cell phones. Luggage and debris were spattered with blood.
There was no immediate indication if suicide bombers were involved. Police inspector Ramesh Sawant said most of the victims suffered head and chest injuries, leading authorities to believe the bombs were placed in overhead luggage racks.
"I can't hear anything," said Shailesh Mhate, a man in his 20s, sitting on the floor of Veena Desai Hospital surrounded by bloody cotton swabs. "People around me didn't survive. I don't know how I did."
Another man, bloody bandages over his eyes, held out a phone to a nurse, begging her to call his wife and tell her he was OK.
A senior Bombay police official, P.S. Pasricha, said the explosions were part of a well-coordinated attack. Vilasrao Deshmukh, the chief minister of Maharashtra state, where Bombay is located, said bombs had caused all seven blasts.
Police reportedly carried out raids across the country following the Bombay blasts. One TV station said a suspect was in custody.