The force of the blast also killed the Pakistani driver of the bus, hurling it down a gorge onto the banks of the River Indus, said Sheraz Khan, station head of the official Rescue 1122 emergency service.
The bodies of the six victims were recovered after the fire on board the wrecked bus was extinguished.
The bus was travelling in a convoy of a dozen vehicles, most of them carrying security personnel guarding the Chinese nationals, when it was struck.
Can Shehbaz Sharif thaw Pakistan-India ties as Kashmir remains sticking point?
Can Shehbaz Sharif thaw Pakistan-India ties as Kashmir remains sticking point?
No terrorist group has yet claimed responsibility for the attack.
In July 2021, nine Chinese nationals working on the World Bank-funded Dasu project were killed in a vehicular suicide bombing.
Local resident Muhammad Hayat Khan said he was at home preparing for afternoon prayers when he heard two explosions.
Upon reaching the nearby highway, he found the burning remains of the bomber’s vehicle and the bus that was targeted.
Besham police chief Juma Rehman said an investigation has been launched.
“We will investigate from where and how the vehicle of the suicide bomber came and how it happened,” he said.
More to follow …
Additional reporting by Tom Hussain