The report said the blast was executed targeting the bus but it is yet to be ascertained whether it was the result of a roadside device or something planted inside the bus.

The blast caused the bus to fall into a deep ravine, Reuters reported citing a senior government official who did not want to be named.

A Chinese engineer and a Pakistani soldier are missing post the incident, the official said.

"The rescue operation is launched and the entire government machinery has been mobilised to rescue the injured by air ambulance,” report quoted the official as saying.

Six Chinese nationals, a paramilitary soldier and one local were killed. Several people were injured, he said, stated the report.

Thirty Chinese engineers were travelling in the bus to the site of the Dasu dam in Upper Kohistan, a senior administrative officer told Reuters..

The Dasu hydroelectric project has been undergoing for several years.

It is a part of the China-Pakistan Economic Corridor (CPEC), a $65 billion investment plan under Beijing’s Belt and Road Initiative wich aims to link western China to the Gwadar sea port in southern Pakistan.