An overcrowded bus plunged off a mountain road into a gorge Monday in northern India, killing 17 people, police said.

"The death toll has gone up to 17. All the bodies have been removed from the gorge," senior police official Sumedha Dwivedi told AFP.

Twenty-one others were injured in the accident in the Sirmaur district of Himachal Pradesh state, 142 kilometres (88 miles) from capital Shimla.

Deadly traffic accidents are common in India. In January, a bus crash killed 27 people in the western state of Maharashtra.

Around 140,000 people were killed in Indian road accidents in 2012 -- which works out to 16 an hour -- according to the government's National Crime Records Bureau.

Bad roads, speeding vehicles and poor driving were among the contributing factors.