The deadly explosion brought down the minister's office trapping 20-25 people including the minister, the Dawn reported. Khanzada's son, Sohrab, told Geo News that his father was present when the blast took place.
Reports later confirmed that Khanzada succumbed to his injuries in what was termed as a suicide attack. The impact of the blast shattered windows in nearby houses.
Minister Khanzada, given charge of the home department in October 2014, was critically injured, hospital sources said. The "entire structure has been destroyed".
A number of the dead were pulled out of the rubble of the building.
The minister has been actively involved in major operations against terrorist outfits. His department is responsible for the maintenance of law and order.
Rescue operations were underway at the scene of the attack, media reports said. A helicopter had been pressed into service.