Indian defence scientists are planning to put one of the world's hottest chilli powders into hand grenades.

They say the devices will be used to control rioters and in counter-insurgency operations.

Researchers say the idea is to replace explosives in small hand grenades with a certain variety of red chilli to immobilise people without killing them.

The chilli, known as Bhut Jolokia, is said to be 1,000 times hotter than commonly used kitchen chilli.

Scientists at India's Defence Research and Development Organisation (DRDO) are quoted as saying the potent chilli will be used as a food additive for troops operating in cold conditions.

And the powder will also be spread on the fences around army barracks in the hope the strong smell will keep out animals.

Other forms of pepper spray are commonly used for crowd control in many parts of the world.