A powerful bomb placed in a briefcase outside the High Court in New Delhi killed at least 11 people and wounded 76 today.
Authorities said the attack was claimed by a South Asian militant group linked to al-Qaeda.
The 2kg bomb left a crater three to four feet deep near the main reception counter where passes are issued for lawyers and visitors to enter the building before the main security checkpoint.
The deadliest attack in India in almost two months prompted the government to put the capital on high alert.
Authorities said the Harkat-ul-Jihad Islami (HUJI) militant group, which has bases in Pakistan and Bangladesh, had sent an email claiming responsibility. Ilyas Kashmiri, who US authorities believe was recently killed in Pakistan, was the head of HUJI and a senior al-Qaeda member.
In an email to the National Investigation Agency, the group called on India to repeal the death sentence of a man convicted in connection with an attack on the Indian parliament in 2001 and warned it would otherwise target major courts in the country.
In May, a low-intensity blast outside the same High Court in Delhi triggered panic but injured no one.
Prime minister Manmohan Singh is on an official visit to Bangladesh, the first visit by an Indian premier in 12 years.
Home minister Palaniappan Chidambaram told parliament: "Delhi is a target of terrorist groups . . . [but] we shall never be intimidated by terrorist groups." He pledged to track down those responsible.
About 120 soldiers, police and bomb squad specialists were at the scene of today's bombing, with ambulances whisking the injured away to hospitals. Television images showed scores of lawyers running from one of the main gates of the building just after the explosion.
The attack in the heart of the capital will renew concern about the authorities' ability to prevent attacks, particularly in sensitive, high-risk areas.
The attack comes less than two months after near-simultaneous triple bomb attacks in India's financial hub Mumbai killed 24.
There is still no word on who was behind the Mumbai attacks, although police have focused their investigation on the Indian Mujahideen, a home-grown militant group know for its city-to-city bombing campaigns using small explosive devices.
Reuters