He said the bomb was set off by remote control.
At least 12 people were taken to hospital for wounds, a doctor at Bannu hospital said.
It is the latest in a series of recent attacks against security personnel in the volatile area.
Violence in Pakistan has increased since Pervez Musharraf stepped down as president more than a week ago.
On Wednesday, Pakistani security forces claimed to have killed more than 40 anti-government fighters, including some foreigners, in the country’s northwest tribal region.