Police say twin explosions in a northwest Pakistani city have killed two people and wounded at least 20 others, including the local police chief.

Police official Saleem Khan says the blasts went off minutes apart on Thursday near a police facility in Bannu, a town near Pakistan’s tribal belt.

The exact nature of the explosions was unclear, and no militant group immediately claimed responsibility.

However, the explosions follow a suicide bombing that killed 17 people, most of them police, in the Khyber tribal region on Wednesday.

Pakistan has waged an Army offensive against Taliban fighters in the tribal areas, while the U.S. has pursued the militants with missile strikes.

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