According eye witnesses, the terrorists tried to enter the courtroom of Additional Sessions Judge and hurled a hand grenade there.
Provisional Information Minister Mian Iftikhar Hussain said there were two suicide bombers; one blew himself up while the other was gunned down by the police.
Iftikhar Hussain feared that some terrorists could be inside the building and several people could be still refugee.
Armed forces and police surrounded the area following the suicide blast. The glasses of several building were smashed due to the intensity of blast.
The injured have been shifted to the Lady Reading Hospital.