Scores of people have been killed in at least seven near-simultaneous bombs on trains in the Indian financial capital, Mumbai (Bombay), police say.
The city's police Chief AN Roy said on Indian TV as many as 100 people were feared killed and more than 250 hurt.
The first explosion went off at about 1830 local time (1300 GMT), during the peak of the evening rush hour in the suburbs on the busy Western Railway.
There have been a number of bomb attacks in Mumbai in recent years.
The city and the capital Delhi have been put on high alert, and Mumbai's entire rail network has been shut down.
Indian Prime Minister Manmohan Singh appealed for calm and described the incidents as a "shocking and cowardly attempt to spread a feeling of hatred".
Pakistani leaders also condemned the blasts as a "despicable act of terrorism".
More coverage at CounterTerrorism Blog here.