A passenger bus has erupted into flames after a motorcycle crashed into it early Friday, killing at least 25 people and injuring several others in southern India. 

The fire tore through the 'luxury' bus within minutes, trapping dozens of passengers as it sped along a highway near Kurnool district in Andhra Pradesh state, senior police official Vikrant Patil said.

Some managed to smash open windows and leap to safety with minor injuries while others were burned to death before help could arrive, Patil said.

The bus with 44 passengers aboard, many of them asleep, was travelling between the cities of Hyderabad in Telangana state and Bengaluru in Karnataka state. 

The official added that 15 people had been rescued and have since been admitted to hospital.  

The accident occurred in Chinnatekuru village near Kurnool, around 130 miles south of Hyderabad.

The motorcycle rammed into the speeding bus from behind and got stuck, Patil said. It was dragged for some distance, causing sparks that engulfed the bus's fuel tank.

'As the smoke started spreading, the driver stopped the bus and tried to put the fire out by using a fire extinguisher, but the fire was so intense he couldn't control it,' Patil said.

Most passengers were asleep at the time of the accident. The bus was gutted and the unidentified bike rider also died, he said.

A team of forensic experts was investigating the incident.

Prime Minister Narendra Modi and Andhra Pradesh's highest elected official, N. Chandrababu Naidu, offered their condolences to the bereaved families.

The deadly bus fire was the second such accident in India in less than two weeks. 

A suspected short circuit sparked a fire on a passenger bus in the northern Indian state of Rajasthan early this month, rapidly engulfing the vehicle in flames and killing at least 20 people.