The blast took place at around 10.15 am. Home secretary RK Singh told reporters the explosives were placed in a briefcase at the high court reception where hundreds of people come through every day to attend court cases.
The government is investigating an email allegedly sent by the Pakistan-based terrorist group Harkat-ul-Jihad Islami claiming responsibility for the blast at the court.
Television images showed scores of lawyers in black coats running from one of the main gates of the building.
"This appears to be a bomb explosion and it is at least a medium-intensity bomb... The site has been fully secured and Delhi has been put on high alert. Whatever precautions need to be taken are being taken," said home ministry official UK Bansal.
The injured have been taken to AIIMS, RML and Safdarjung hospitals. The Delhi Police have cordoned off the area, not far from Parliament and the Prime Minister's Office. Fire tenders have been rushed to the spot.
Top officials of Delhi Police including Special Commissioner (law and order) Dharmendra Kumar and Joint Commissioner of Special Cell RS Krishnaiah have rushed to the spot.
Jt Commissioner (Crime) Sandip Goyal and Special Commissioner PN Aggarwal also joined them.
Rajya Sabha has been adjourned till 2pm to allow government collect information and make its statement on bomb blast outside Delhi High Court.
The blast was the second explosion at the high court this year. On May 25, a small explosion that appeared to be a failed car bomb hit the court parking lot.
A high alert in the capital has been sounded and security tighten at public places.
DELHI HIGH COURT BLAST LIVE UPDATES
01:31pm: MHA sources say an IED was used for the blast
01:20pm: Delhi chief minister Sheila Dikshit visiting RML hospital to see the injured
01:15pm: Home minister visits blast site, on way to hospitals to see the injured
01:06pm: PM sends condolences to the family members of those killed
01:06pm: PM calls the Delhi blast a cowardly attack
01:05pm: Prime Minister makes first statement on Delhi blast from Dhaka
12:52pm: Delhi Lt Governor condemns blast, says Delhi 'lucrative' target for terrorists
12:49pm: LK Advani says, "We are all united in this moment of crisis"
12:48pm: LK Advani condemns Delhi blast
12:46pm: Senior BJP leader LK Advani makes statement
12:44pm: Home minister confirms 9 dead, 47 injured
12:43pm: Home minister calls the Delhi blast a terror attack
12:40pm: Home minister P Chidambaram makes statement in Parliament
12:08pm: So far 9 people confirmed dead. Casualties may go up
12:06pm: At least 50 injured people brought to RML Hospital
11:57am: Blast helpline numbers: Safdarjung Hospital - 011-26707444, RML Hospital - 011-23744721
11:52am: All metros put on high alert
11:50am: Home minister to make statement at 12:30pm
11:48am: Reports say death toll now stands at 11
11:45am: 9 killed, 45 injured
11:43am: Home secretary calls for emergency meeting on the blast
11:38am: Police confirms 27 injured
11:29am: NSG squad reaches spot
11:25am: 9 people confirmed dead
11:22am: Home minister to make statement in Parliament
11:20am: Home ministry assesses situation
11:12am: Police say blast took place outside the court premises
11:10am: Police sources say bomb was kept in briefcase
10:59am: At least 4 people are reported killed
10:46am: Delhi police commissioner reaches blast site
10:45am: Injured rushed to nearby hospitals like Ram Manohar Lohia Hospital, Safdarjung Hospital and Lady Hardinge Medical College and Hospital
10:35am: Entire area cordoned off
10:28am: Sources confirm at least 20 people are injured
10:23am: At least 7 people reported injured
10:20am: Many people reported injured
10:15am: Blast outside Delhi high court