A powerful bomb placed in a briefcase outside the high court in New Delhi killed at least 10 people and wounded 50 on Wednesday in an attack authorities said was claimed by a Bangladeshi-affiliated Islamist group.
The bomb dug a crater three to four feet deep near the main reception counter where passes are issued for lawyers and visitors to enter the sprawling sandstone building before the main security checkpoint.
Authorities said the outlawed Harkat-ul-Jihad Islami (HUJI) militant group, with bases in Bangladesh and Pakistan, had sent an email claiming responsibility.
Minister Manmohan Singh is currently on an official visit to neighbouring Bangladesh, the first visit by an Indian prime minister in over a decade.
"That mail has to be looked at very seriously because HuJI is a very prominent terrorist group among whose targets India is one," National Investigation Agency (NIA) chief S.C. Sinha told reporters.
In an email to the NIA, 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 who was awaiting execution by hanging.
The blast comes as security has been stepped up at key locations as parliament is in session and ahead of the anniversary of the Sept. 11, 2001, attacks in the United States. It also 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.
"I was near the gate at that time," said lawyer K.K. Gautam. "There was an orderly queue when a loud blast occurred. I saw many injured and dead. I saw 20-25 injured and around 10 dead.'
The court building compound is in a leafy, usually tranquil and upscale part of the city. The outside gate is usually manned by a handful of policemen armed with automatic rifles and hand-held scanners.
Lawyers in black suits and starched white collars stood around shocked on one of the busiest days of the week when the court hears public interest petitions.
About 120 soldiers, police and bomb squad specialists were at the scene, 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. Police cordoned off the area, not far from parliament and the prime minister's office.
"I think I saw this guy (suspect). He was in white, aged 34 or 35, carrying a briefcase and jumping the long queue," a middle-aged man told Indian television channels.
"There must have been some 80 people at that time when the bomb went off. I crouched immediately but the man behind me, he did not and was hit (by shrapnel) to his right arm."
The blast in the heart of the capital will renew concern about the authorities' ability to prevent attacks, particularly in sensitive, high-risk areas.
"This is a glaring example of the shortage of intelligence, both human and technical -- something if we had had we could have prevented these attacks," said Ajai Sahni, executive director at the Institute for Conflict Management in New Delhi.
Two lawyers at the court, Namita Roy, 48, and Hargovina Jah, 40, told Reuters the scanner and metal detector at Gate 5 of the court where the blast occurred were not working.
"This is definitely a big security lapse on the part of the police. For example, yesterday even the (body) scanner was not working. The security, more or less, is very weak, especially in view of the blast that happened a few months ago," said Roy.
The blast outside the court, seen as a high profile but soft target, comes at a time when the judiciary is in sharp focus for nudging the government to act on issues ranging from corruption to the environment.
Congress party politicians have over the past year criticised the Supreme Court for overstepping its authority and intervening in executive functions.
"So an attack on such a target will bring you the maximum mileage," said independent strategic analyst Maj. Gen. Ashok Mehta. "Also, notice that this comes just days before 9/11, so the government should have expected something like this."
Several bomb attacks in large cities in recent years have been tied to the Indian Mujahideen, said to have support from Pakistan-based militants.
In May, a low-intensity blast outside the same High Court in Delhi triggered panic but injured no one. Pakistan-based militants attacked Mumbai in coordinated assaults that killed 166 people in 2008, raising tensions with nuclear-armed arch rival Pakistan.
Prime Minister Manmohan Singh and his government came under intense criticism over the handling of those attacks. The government promised a radical overhaul of the security apparatus in India but critics say the reforms have been inadequate and in some cases abandoned.