PESHAWAR (Reuters) - A bus veered into a ravine in Pakistan's far north early on Friday, a local government spokesman said, killing 20 passengers, while 21 injured were rescued and taken to hospital.

The bus was headed to the mountainous northern area of Gilgit-Baltistan from the garrison city of Rawalpindi in Pakistan's eastern province of Punjab, when the accident happened in the early hours.

"The bus was passing through Diamer district in Gilgit-Baltistan when it fell into a deep ravine," Faizullah Firaq, a spokesman for local government authorities in the area, told Reuters, adding that 21 people were injured.

The government immediately launched a rescue operation to evacuate all the injured, who were taken to hospital, he added.

Fatal road accidents are common in Pakistan, where traffic rules are rarely followed and roads in many rural areas are in poor condition.

For decades Pakistan has done extensive work in carving roads through its dramatic rugged northern terrain, home to some of the world's highest mountain ranges, approached by narrow roads perched on sheer cliffs.

Militant attacks, including one in March nearby in Khyber Pakhtunkhwa that killed six people, pose another risk to travellers in the area, targeting Chinese-backed dams and hydropower infrastructure projects.

(Reporting by Mushtaq Ali in Peshawar; Writing by Charlotte Greenfield; Editing by Clarence Fernandez)

By Mushtaq Ali