Four students were killed in a freak road mishap on the outskirts of Chennai, capital of the southern Indian state of Tamil Nadu, on Monday, a police official said.

"The mishap happened this morning at Perungudi when a reversing truck brushed against a bus on which the victims were traveling. The four students were actually standing on the foot-board of the bus and were caught between the bus and the truck," he said, on condition of anonymity.

While three students were killed on the spot, the fourth victim succumbed to injuries on the way to hospital, the official said.

A probe has been ordered into the incident, he added.