Najib Danish, deputy spokesman for the Interior Ministry, says that at least 10 people were also wounded in Tuesday's bombing.
He added that the explosion took place near a side door, which is used by the court's employees to leave the building, and not the main entrance, the Associated Press reported.
No one immediately claimed responsibility for the attack in the Afghan capital but Taliban insurgents have attacked the top court and its employees in the past, as well as court buildings in the other provinces.