NEW DELHI, India — At least 150 people were killed and hundreds injured yesterday when seven bombs exploded on Mumbai’s crowded commuter network.

The closely coordinated attacks were quickly attributed to Islamic militants with links to the disputed territory of Kashmir.

The blasts tore through five trains and two stations at evening rush hour. The first explosion burst open the first-class compartment of a train on the Western Expressway. Six more explosions followed over 20 minutes, sending commuters jumping from the slow-moving trains and racing for cover.

Bodies littered the tracks and the injured were lifted from the twisted wreckage by anyone prepared to lend a hand. Telephone links were rapidly overwhelmed as desperate commuters tried to contact families and friends.

India’s major cities, including New Delhi, Calcutta, and Bangalore, were put on “high alert” as Prime Minister Singh met security officials.

India’s financial capital was left paralyzed and in panic after the attack, designed to cause maximum disruption to a city whose infrastructure is already woefully inadequate.

The seven bombs that left around 150 people dead and more than 400 injured were spread out along the entire length of Mumbai’s Western Expressway.

The toll from the carefully coordinated attack was inevitably high. The commuter rail route is a transport lifeline that is the backbone of one of the world’s most congested cities, and its trains are packed to the point where hundreds hang from doors and windows.

The first blast came at 6:25 p.m. local time. It burst open the first-class compartment of a train carrying a tiny fraction of the 6 million people who travel on Mumbai’s railways every day.

“The blast was so powerful that we thought we were hit by lightning. It shook our market,” a local shopkeeper, Gopi Chand, said. “The fourth carriage was completely wrecked.”

Six more explosions on trains and at two stations followed over a terrifying 20-minute period. As darkness fell, Mumbai’s emergency services, rudimentary by Western standards for a city of 17 million people, struggled to reach the bomb sites through congested streets and driving monsoon rains.

The attacks are the worst to hit Mumbai since August 1993, when 260 people were killed in a series of bomb attacks attributed to Muslim-dominated underground gangs.

Confirming the deaths had exceeded 100, Mumbai’s police commissioner, A.N. Roy, said his men were working desperately to rescue the injured. “Obviously a terrorist outfit is behind the blasts because a normal human being could not have done this,” he added.

Business leaders were concerned that Mumbai’s benchmark Sensex stock exchange, already suffering losses over the last two months, would plunge still further when it reopens.

Indian security sources said the attacks were clearly aimed at derailing recent attempts to hold talks with separatist parties in Kashmir, the disputed border territory that has caused three wars between India and Pakistan since partition in 1947.

Officials said the coordinated nature of the attacks bore the hallmarks of the Islamic extremist groups Lashkar-e-Toiba, or Army of the Righteous, and Jaish-e-Mohammad, or Army of Mohammad, that have been active recently in India.

The train bombings came hours after a series of grenade attacks in Srinagar, the capital of Indian-controlled Kashmir, that killed eight people.

Fears that terrorist attacks could destabilize relations between Pakistan and India have eased considerably following a period of detente. Pakistan, which came to the brink of a nuclear confrontation with India following a terrorist attack on the Indian parliament in December 2001, was quick to condemn the attacks as a “despicable act of terrorism.”

Mr. Singh called for calm after an emergency meeting at his official residence.

“We will work to defeat the evil designs of terrorists and will not allow them to succeed,” he said.