The death toll of the terrorist attack outside the Delhi High Court in the Indian capital Wednesday has risen to 11 while 76 people were injured, a senior Home Ministry official said.

The attack is described as the third worst bombing attacks since the Mumbai terror attacks in 2008.

Police said a suitcase bomb went off around 10.30 a.m. just outside Gate No. 5 of the Delhi High Court complex near India Gate, a major tourist attraction, in central New Delhi where about 300 people including litigants, media personnel and other visitors to the court were queuing to get passes for entry into the court.

Indian Home Secretary R.K. Singh said the remains of the suitcase where the bomb was have been found.

The Pakistan-based Harkat-ul-Jehadi Islami in an email to various media houses claimed responsibility, according to Indo- Asian News Service.

The email sent from an unknown location threatened that the hanging of 2001 parliament attack convict Afzal Guru should be repealed immediately, according to the news service. But this report is not confirmed by the authorities.

"We are investigating how the brief case was placed there as it is not a controlled area. There were lots of people," said Special Commissioner Dharmendra Kumar.

Delhi Police Commissioner B.K. Singh has rushed to the spot which has been evacuated as local TV channels aired footage of commandos taking over the building complex located near the iconic India Gate in central Delhi.

According to TV channels, Delhi Police suspect use of potassium nitrate in the blast.

Indian Prime Minister Manmohan Singh condemned the attack as cowardly and called on all political parties, all the people of India have "to stand united so that the scourge of terrorism is crushed".

In May this year, a blast took place in a parking lot near the cafeteria of the High Court. At that time, no body was injured.