NEW DELHI, Jan. 20 (Xinhua) -- At least seven people have been killed and 20 others injured in a road accident in the eastern Indian state of West Bengal Saturday, police said.

"The accident occurred when a passenger bus veered off the road and overturned on a highway at Beldanga in the state's Murshidabad district this morning," a senior police official said.

While seven passengers died on the spot, those injured were admitted to a government hospital by local people and police, where the condition of nine people were said to be serious, he said.

Eye-witnesses told cops that the bus was travelling at high speed and the driver suddenly lost control of the vehicle, leading to the accident.

"A probe has been ordered into the incident," the official added.

The accident came three days after six people were killed and 25 others injured when a bus in which they were travelling fell into a roadside ditch in the state's West Midnapore district.

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.