A bus driver who killed nine people and injured 30 in a rush-hour rampage may have been drunk, according to doctors.

Santosh Mane, 30, a licensed bus driver in the western Indian city of Pune, took an empty bus from the Swargate depot and drove it in a 30-minute rampage through rush-hour traffic, police said.

Doctors who examined Mane at Pune hospital told NDTV that he was "most likely drunk". Mane reportedly told doctors he had been undergoing psychiatric treatment.

Pedestrians fled in panic as more than 40 vehicles were smashed during Mane's rampage, which saw him veer on to the wrong side of the road, crushing vehicles and pedestrians alike.

He was eventually overpowered by pedestrians, including college student Sharif Kutty, who restrained him when his bus stalled.

Three doctors who examined Mane at a Pune hospital have told NDTV that he appeared drunk.

He had been a driver for the government-run transport department for 11 years. Police are continuing to investigate his motive.

"We don't know why the driver behaved like this. He just went berserk. We are trying to find out the reason," said police chief Meeran Bowankar.