The blast left 17 others injured, reports said.

As per Geo News report, the blast occurred near a police truck parked close to GPO Chowk on Zarghoon Road, located in the city's high-security Red Zone, around 300 metres from the provincial assembly building.

Security forces were returning after their routine tasks when the blast occurred. Police and bomb disposal squad have reached the spot after the blast.

The nature of the blast is still not known.

Geo News reported a bus, which was located close to the spot, was also damaged due to the blast.

The area has been cordoned off.

The injured people have been shifted to  Civil Hospital Quetta.