(CNN) -- Up to 20 people were killed when about 15 to 17 blasts rocked the western Indian city of Ahmedabad within a little more than an hour Saturday night, police and government officials said.
The explosions were mainly concentrated in the eastern part of the city, all within a 10-kilometer (6.2-mile) radius, according to CNN's sister network, CNN-IBN. Dozens were injured.
Several media outlets and the country's Intelligence Bureau received an e-mail purportedly from the militant group Indian Mujahedeen warning about a possible attack.
Indian Mujahedeen claimed responsibility in May for near-simultaneous bomb attacks that killed 63 people in the northwest Indian city of Jaipur. In the Jaipur claim, the group declared "open war" against India in retaliation for what it said were 60 years of Muslim persecution and the country's support of U.S. policies.