The cause of the accident was unclear, and rescue workers were still working at the scene recovering the injured and the dead and taking them to a nearby hospital, said Faiz Ullah Faraq, spokesman for the Gilgit Baltistan region.
Such accidents are common in Pakistan, mainly due to insufficient enforcement of safety standards and poor infrastructure, particularly on battered mountain roads.
Faraq said the bus had been headed to the town of Skardu in the Gilgit Baltistan region from the garrison city of Rawalpindi. He gave no further details.
Skardu serves as the gateway to K-2, the world's highest peak after Mt. Everest, which is also part of the Himalayas. Large numbers of local and foreign tourists visit the peak annually. Skardu is around 240 kilometers (150 miles) north of the Pakistani capital of Islamabad.