Indian federal investigators examined yesterday two unverified claims by militant groups that they were behind a deadly bomb blast at New Delhi's High Court that left 12 people dead.

One emailed claim purportedly sent from Harkat-ul-Jihad al-Islami (HuJI), a Pakistan-based Islamist militant group, was traced to an Internet cafe in Kishtwar, a town in the volatile Muslim-majority region of Indian Kashmir.

Local police told AFP that two brothers who owned the cafe and one employee were taken in for questioning, but

no formal arrests had been made.

A separate email sent to media organisations yesterday said the bomb was the work of the home-grown Indian Mujahideen outfit and threatened another attack on a shopping mall next week

Neither claim was confirmed by police as genuine, but Internal Security Secretary UK Bansal said intelligence agencies were "seriously examining" both mails.

Wednesday's powerful blast ripped through a crowd of litigants queuing to enter the court complex in the heart of the Indian capital, killing 12 people and injuring nearly 80.

It was the latest in a long list of bombings in Indian cities and prompted searching questions in the national media about the authorities' inability to prevent such attacks and bring the perpetrators to justice.

Police separately released sketches of two suspects seen at the site of the blast.

"We have some leads but it is too early to say wJiich group is behind it," Prime Minister Manmohan Singh told reporters on his plane as he returned late Wednesday from an official visit to Bangladesh.

"There are obviously unresolved problems and weaknesses in our system and the terrorists are taking advantage of that," Singh said. "We must work hard to plug those weaknesses," he added.

With some experts suggesting the May attack had been a dry run for Wednesday's blast, a number of editorials in the national press questioned why security at the court had not been effectively tightened.

"With cars spilling out of the car park and no security check worth its name installed, it was a veritable invitation for anyone seeking to perpetrate violence," said the Hindustan Times.

Highlighting the fact that no blast case in the last two years has been solved, The Times of India said it was "truly shocking" that the court could have been successfully targeted twice in such a brief space of time.

"This speaks of an extraordinarily lax security culture,” the Times said.

Home Minister P Chidambaram held a high-level meeting yesterday at which National Security Advisor Shivshankar Menon was also present to take stock of the situation.

The United States, France, Britain and Pakistan all condemned the bombing, with Washington describing it as "cowardly".