Although initial reports suggested the blast was caused by an Improvised Explosive Device, police sources later said it was a suicide attack targeting the vehicle. The blast took place in Chaman city in Balochistan located near the Afghan town of Spin Boldak, Dawn News reported.
District Police Officer Killa Abdullah Sajid Mohmand, who was critically wounded in the blast, succumbed to his injuries in the hospital. Two others were also killed in the attack.
Police officers and passers-by were among those wounded in the attack, the report said.
An emergency has been declared in hospitals and law enforcement and rescue officials have been dispatched to the site of the incident.
Interior Minister Chaudhry Nisar and Balochistan Home Minister Mir Sarfaraz Ahmed Bugti condemned the attack. Mr Nisar sought a report probing the incident.
Chaman is considered a sensitive town in Balochistan as it shares a border with Afghanistan's volatile Kandahar province.