A blast on a bus killed 13 people in north Pakistan on Wednesday, including nine Chinese nationals in what Beijing said was a bomb attack but Islamabad called a vehicle failure.
Two Pakistani soldiers were also among the dead after the explosion sent the bus over a ravine.
Chinese engineers and Pakistani construction workers have for several years been working on hydroelectric projects as part of Beijing's Belt and Road Initiative in the western province of Khyber-Paktunkhwa, where the blast occurred.
China's embassy in Pakistan confirmed that nine of its nationals died. Terming the explosion a bomb attack but not giving more details, the Chinese foreign ministry offered condolences and urged both a thorough investigation and protection of its personnel and projects.
Pakistan's foreign ministry said a mechanical failure caused a gas leak which led to the explosion.
However, the province's top police official, Inspector General Moazzam Jah Ansari, earlier said foul play was suspected. "Looks like sabotage," he said.
A senior administrative officer of the Hazara region, who asked not to be named, said the bus was carrying more than 30 Chinese engineers to the Dasu dam in Upper Kohistan.
The Dasu hydroelectric project is part of the China-Pakistan Economic Corridor (CPEC), a $65 billion investment plan aiming to link western China to the southern Pakistani port of Gwadar.
