PARACHINAR: A government official says gunmen have killed ten bus passengers in an ambush in northwest Pakistan.

The official Mohammed Ali said three people were also injured in Saturday's attack in the Upper Kurram region bordering Afghanistan.

He said the dead and injured had been transported to a hospital.

Ali says it's not immediately clear who were behind the attack and an investigation is under way.

Kurram has witnessed scores of such attacks and kidnappings for ransom in the past several years.

The military has launched offensives against Taliban militants there, but violence has continued.