Indian authorities have arrested hundreds of people and cancelled more than 300 trains passing through two northern states after at least 29 people were killed in violent protests following the conviction of a self-styled 'godman'.

Security forces were on "standby" outside the spiritual leader's headquarters where some 10,000 followers remained holed up, the Director General of Police in Haryana state, Baljit Singh Sandhu, told India Today news station.

Gurmeet Ram Rahim Singh, the head of a social welfare and spiritual group with a wide following in Punjab and Haryana states, was found guilty on Friday of raping two followers in a case dating back to 2002 at the headquarters of his Dera Sacha Sauda group in the northern town of Sirsa.

Supporters rampaged in response, attacking railway stations, petrol stations and television vans in towns across the northern states of Punjab and Haryana, witnesses said.

At least 29 people were killed in Panchkula town where the court returned its verdict on Singh and more than 200 people were injured, mainly in Haryana state.

The protests, about 250 km (155 miles) from the Indian capital New Delhi, was one of the biggest this year related to a 'godman' spiritual leader.

About 524 people had been arrested, Ram Niwas, a top Haryana administrator, told Reuters.

Authorities said they were bracing for Singh's sentencing on Monday when there could be more violence.

A spokesman for the northern division of Indian Railways said 340 trains have been cancelled on Saturday as a precaution.

"We're monitoring the situation but we may have to cancel more trains," Neeraj Sharma told Reuters.

Security personnel were still guarding Panchkula, which was among the worst affected towns during the violence, as some shops started to reopen and people came out of their homes.

"I was just speaking with an army general to continue patrolling in Sirsa," said Niwas.

"We've asked everyone to continue effective patrolling, because the (sentence) will be announced the day after."

Singh is also under investigation over allegations that he convinced 400 of his male followers to undergo castration. He denies those charges.