At least 10 people, including at least six Chinese nationals and two Pakistani soldiers, were killed in a blast targeting a bus in a remote region of northern Pakistan on Wednesday, multiple sources told Reuters, adding that the toll could rise.

It was not immediately clear whether the blast was the result of a roadside device or something planted inside the bus.

Inspector General Moazzam Jah Ansari, the top police official of Khyber-Paktunkhwa, the province in which the incident occurred, confirmed the death of six Chinese nationals, two soldiers and two locals.

"The bus plunged into a deep ravine after the blast and caused heavy losses. One Chinese engineer and one soldier are missing. The rescue operation is launched and the entire government machinery has been mobilised to rescue the injured by air ambulance," a senior government official told Reuters on condition of anonymity.