Security officials gather around a damaged police bus at the site of suicide bomb attack in Quetta.
Five police personnel and a passerby were killed and 16 others injured on Tuesday when a suspected suicide bomb rocked Quetta's Zarghoon road near the Balochistan Assembly building.
The attack took place near the legislative assembly of Balochistan province.
The Assembly session had just finished and all the MPs had left the Assembly.
The suspected suicide bomber was travelling on a motorbike. His target was Balochistan Assembly building but was stopped at security post where he exploded himself.
The security forces immediately cordoned off the blast site, whereas, rescue teams rushed to the spot and moved the injured persons to nearby hospitals.
"At least five policemen and a pedestrian were killed and 16 others were wounded when a suicide bomber on a motorcycle struck the bus," senior police official Abdul Razzaq Cheema told AFP.
There were no immediate claims of responsibility for the attack, he added.
Quetta is the capital of Balochistan province, which borders Iran and Afghanistan and has oil and gas resources but is afflicted by Islamist militancy, sectarian violence and a separatist insurgency.
Police and troops have been battling Islamist militants and separatist groups in mineral-rich Balochistan for more than a decade.