India faced up to a massive security failure as the main nationalist opposition party on Sunday declared the country to be at war with Islamist militants who claimed responsibility for devastating bomb attacks on New Delhi.

The bombings, which killed 21 people in the space of half an hour on Saturday evening, were claimed by the Indian Mujahideen. The little-known Islamist militant group, which sent an e-mailed warning from a hacked company address in Mumbai, has also claimed responsibility for blasts in Bangalore, Ahmedabad and Jaipur in the past three months.