China has asked Pakistan to thoroughly investigate a bus blast that killed nine Chinese nationals, China's Foreign Ministry spokesperson Zhao Lijian said on Wednesday.

China strongly condemns the blast, and extends its condolences to the victims and their families, Zhao said.

A total of nine Chinese and three Pakistani nationals were killed in the blast, said the Chinese Embassy in Pakistan. Local media reported that four Pakistani nationals died in the blast.

Local media quoting officials said that a bus carrying workers to a working site in the Dasu area of the Upper Kohistan district was hit by a blast on Wednesday. 

Security forces, police and rescue teams rushed to the site and shifted the bodies and the injured to a nearby hospital.

(With input from Xinhua)