"Indian Mujahideen" claimed the responsiblity of the blasts

A group called the "Indian Mujahideen" said it carried out the Ahmedabad attack, writing in an e-mail sent five minutes before the first blast that it was in revenge for a 2002 massacre in Gujarat of around 2,500 people, mainly Muslims, by Hindu mobs.
The email sent to various news media read"Do whatever you can, within 5 minutes from now, feel the terror of Death!"
The email from the Indian Mujahideen warned the governments of several states to stop harassing, imprisoning and torturing Muslims and told media outlets to stop their "propaganda war" against Muslims.
It also warned Mukesh Ambani, chairman of Reliance Industries and one of the world's richest men, to think twice before building a luxury 27-storey home on land in Mumbai previously owned by a Muslim charity.
Police also traced the Indian Mujahideen e-mail to a computer belonging to an American, living in a Mumbai suburb, who has been questioned. Local media said his computer may have been hacked.