At least two policemen were killed and 12 people, including eight policemen, injured on Sunday when a powerful blast targeted a police van near a luxury hotel in Quetta, the capital of Pakistan's troubled southwestern Balochistan province, officials said.
"The initial probe showed that the bomb was fitted with a motorbike," Balochistan government spokesman Liaquat Shahwani said.
He said the blast killed two policemen and wounded eight others.
Shahwani said four passers-by were also wounded in the blast that targeted the police mobile van at Tanzeem Square near Serena Hotel in Quetta.
The security agencies have cordoned off the area and launched a manhunt to arrest the culprits, he added.
The injured have been shifted to the city's Civil Hospital, a senior police official said, adding that the windows of nearby buildings were shattered due to the explosion.
No group took the responsibility for the blast but the Baloch nationalists are active in the province and often target the security forces. They accuse the federal government of exploiting the natural resources of the province.