Jibran Ahmad & Syed Hassan

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.

However, the Ministry of Foreign Affairs claimed in a statement that the bus plunged into a ravine and killed 9 Chinese and three Pakistanis on board.

The MOFA claims the bus malfunctioned "after a mechanical failure, resulting in leakage of gas that caused a blast".

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.

Ansari told Reuters that police were investigating.

"Looks like sabotage," Ansari said as he was departing on a helicopter for the site.

At least three other officials confirmed to Reuters that a blast hit the bus.

China has asked Pakistan to thoroughly investigate a bus blast that killed at least 10 people, including Chinese nationals, on Wednesday, the foreign ministry said.

Beijing condemned the blast, expressed condolences and asked Pakistan to protect the safety of Chinese personnel, institutions and projects, foreign ministry spokesman Zhao Lijian told a regular news briefing.