A car loaded with explosives was the cause of the explosion according to the police.
Police offcials have surrounded the area of the blast.
At least 20 people, among them six policemen, were killed when a suicide bomber rammed his explosive-laden vehicle into a mosque next to a police station in Bannu last month.
Police officials and security forces have been the target of attacks that have been blamed on terror networks linked to the Taliban and al Qaeda.
Around 4,000 people have died in suicide and bomb attacks across Pakistan since 2007.
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