Police say six school children and their bus driver have been killed as the vehicle rolled down a gorge on a hilly road in northern India.

Police officer Rohit Malpani says another 12 children have been hospitalized with injuries as the school bus skidded off the road in Himachal Pradesh state on Saturday.

Malpani said three students in age-group 5 to 14 and the bus driver died on the spot. Three students died later in a hospital.

The cause of the accident is being investigated.

Around 150,000 people die every year on India's roads, often because of reckless driving, badly maintained roads and vehicles overcrowded with passengers.

In September, 55 people were killed when a bus carrying pilgrims from a Hindu temple in the hills of south India plunged off a road.