The blast is the second one in two months at Delhi High Court and the entire area has been cordoned off and police have asked people to clear the area.
Top officials of Delhi police including Special Commissioner (law and order) Dharmendra Kumar and Joint Commissioner of Special Cell R S Krishnaiah have rushed to the spot.
Jt Commissioner (Crime) Sandip Goyal and Special Commissioner P N Aggarwal also joined them.
Kumar said it was too early to ascertain the exact nature of the blast.
He declined to speculate whether the blast was of low intensity or high intensity.
It is in the second time in four months that a blast occured outside the Delhi High Court complex.
An explosion on May 25 triggered panic prompting the authorities to sound a high alert in the capital and tighten security at public places. No one was injured.
Low-intensity explosives, wrapped in a polythene bag and kept close to the car parked near Gate No. 7, went off around 1.30 p.m.
Ammonium nitrate, a battery-like object, wires and some nails were found at the site by forensic experts.