Mohammad Riaz Khan, the district police chief, said two women and two children were among the dead.
No one has claimed responsibility for the attack.
Since 2001, the tribal region has been a haven for Taliban fighters blamed for surging violence in both Pakistan and Afghanistan.
Violence has been reported across the northwest after the army launched its operations to flush out Taliban fighters from their strongholds in the region.
Pakistan's military launched a series of offensives against the fighters in the northwest in late April prompting a string of revenge attacks.
However, there had been a lull in the deadly bombings in the past one month.