Pervez Rafi Bhatti, a deputy inspector-general of police, said: "There have been raids in Quetta and other parts of (southwestern Baluchistan) province overnight in which more than 10 people have been arrested."
"More arrests are expected," he added.
The bomb, which exploded next to an army truck in Quetta on Friday, also injured at least 27 people.
Two army personnel were among the dead.
A nationalist group, the Baluch Liberation Army (BLA), claimed responsibility, saying that the army personnel were its target.
BLA spokesman Azad Baluch told reporters by telephone: "Civilians are not our target."
"The bombing is a warning to the government to stop the construction of new cantonments and Gawadar (deep sea) port in Baluchistan," Baluch said.
"Civilians are not our target. The bombing is
a warning to the government ... "
The BLA has claimed similar attacks in the past.
Baluch nationalists are demanding greater political and economic rights for their province. But officials say they lack popular support and were backed only by a handful of tribal chiefs.
Baluchistan is home to hundreds of thousands of Afghan refugees, and Pakistani security forces have deployed thousands of troops along the Afghan frontier to stop cross-border movements by the Taliban and smugglers.