NEW DELHI, Jan 21 (AFP) - Prisoners in an Indian state who attend yoga classes will be freed early because the lessons improve self-control and lessen aggression, authorities there said Thursday.

For every three months spent doing sun salutations, deep breathing exercises and balance postures, a prisoner will get 15 days off their sentence, Madhya Pradesh state's inspector general of prisons told AFP.

"Yoga is good for maintaining fitness, calming the behaviour, controlling anger and reducing stress," Sanjay Mane said.

"When a prisoner attends yoga sessions and fulfils some other conditions, he will be considered for a remission if his jail superintendent recommends his case."

Attending literacy classes and earning college degrees would also bolster a prisoner's case for early release, Mane said.

About 400 prisoners have signed up for the pilot programme at Gwalior city jail.