Police reinforcements were being sent on August 8 to Pakistan's troubled southwestern province of Baluchistan after an attack a day earlier near the town of Turbat killed four police officers and wounded 14 others.
Authorities say militants planted an improvised explosive device on the roadside about 1,000 kilometers west of Quetta and detonated it as a police transport vehicle was passing by.
The bombing comes a month after six gunmen in Turbat attacked a restaurant and killed 18 people from Pakistan's Punjab Province.
Police and security forces are frequently attacked in insurgency-plagued Baluchistan, which borders Afghanistan and Iran and is one of the most deprived areas of Pakistan.
Baluch rebels rose up in 2004, demanding political autonomy and a greater share of revenues from the sale of Baluchistan's oil, gas, and mineral resources.
Based on reporting by AFP and Dawn