NEW DELHI, Jan. 3 (Xinhua) -- At least five people have been killed and more than 12 others injured in a road accident in the western Indian state of Rajasthan Wednesday, police said.

"The accident occurred when a tractor trolley collided head-on with a speeding bus in the state's Sikar district, some 100 kms from Rajasthan's capital Jaipur, this morning," a senior police official said.

The impact of the collision was so severe that five people were killed on the spot, while those injured have been admitted to a nearby hospital, where the condition of four are said to be critical, he said, adding the victims included passengers of both the vehicles.

Police said that preliminary probe has revealed that it was the fault of the bus driver as he was driving at a high speed and lost control of the vehicle while overtaking another vehicle and hit the tractor trolley coming from the opposite direction.

"A probe has been ordered into the incident and we will book the bus driver for rash and negligent driving once the report comes. We have seized both the vehicles, but the front portion of the bus has been badly damaged," the official said.

India has the highest number of road fatalities in the world. Road accidents occur mostly due to poor driving or badly maintained roads and vehicles.