This is the dramatic moment a bus crashed killing at least 12 passengers in Indonesia.

CCTV footage shows the coach driving at high-speed through a junction before overturning in West Kalimantan, at 9:15 am local time on May 6.

Locals were heard screaming as the vehicle overturned, with villagers rushing to save the passengers inside.

Police arrived at the scene, where the bus, operated by Indonesian autobus company Antar Lintas Sumatera, was lying on its side. Traffic was diverted as rescue teams extracted the commuters and driver.

Inspector Indra, head of the Padang Panjang Police Traffic Patrol Unit, said: 'The suspected cause of the accident is brake failure while the bus was going downhill in the Bukit Surungan area.'

Abdul Malik, head of the Padang search and rescue team, said: 'At 12 noon, from the information in the field, 12 people out of 48 passengers were killed.'

The survivors were rushed to the Padang Panjang Regional Hospital, Yarsi Hospital, and nearby community health centres for treatment.

Local media reported that the route was notorious for causing traffic accidents due to its steep terrain and sharp bends.

The bus driver and conductor have both been detained for questioning, authorities said.