Screengrab of spectators after the blast.
At least four of the dead were personnel of Pishin police.
"The bomb was planted underneath the police van, which exploded while the officials were performing routine checks," said district police chief Mehboob Rasheed.
He said the blast also wounded five people including passengers of a minibus.
A senior local administration official Zahid bin Maqsood confirmed the incident and the casualties.
"The roadside bomb was detonated by remote control as a police van reached the site near Saranan area that was patrolling on Quetta-Chaman highway," police said.
The dead and injured were taken to hospital. Later, the injured were shifted to Quetta due to their serious condition.
The law enforcement agencies cordoned off the entire area to trace the suspects. Further probe was underway.
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