Large crowds turned out in India on Wednesday for the last day of the six-week Maha Kumbh Mela, with authorities saying it drew a total of 663 million people seeking absolution of their sins by taking a dip in waters that devout Hindus consider sacred.

Television images showed security officials trying to direct visitors around barricades in the temporary township set up in Prayagraj, close to the banks where holy rivers meet.

"There is a huge rush because it is the last day for all devotees to take a 'holy dip'," said Rahul, a devotee who gave only his first name.

"Thankfully, we were lucky enough to take a holy dip today."

Authorities added security and enforced traffic curbs for the last day after many visitors complained of massive crowds that have choked traffic, leading to jams stretching for kilometres.

India has touted the Maha Kumbh, or Great Pitcher Festival, held once in 12 years, as a key religious event setting world records for the largest gathering of people.

As many as 15.3 million people bathed on Wednesday, said authorities in Uttar Pradesh state, home to the festival, taking the total figure to more than 663 million, or nearly twice the population of the United States.

The last event in 2019 drew 240 million visitors, but this year's event, signified by the term "maha", or great, is rendered still more auspicious by a rare alignment of celestial bodies after 144 years.

Indians from Prime Minister Narendra Modi and ministers to business tycoons and television and film actors participated.

"People from every section and every region of society united in this Maha Kumbh," Modi said on X.

However, a stampede that killed dozens of people and injured several on the festival's most auspicious day last month marred authorities' efforts to ensure it went off smoothly.

Police officers charged with managing the crowds said the AI-based software they used to track visitor numbers also flashes alerts upon detecting a crowd surge in any area, a fire, or unscheduled barricade crossings.

Devout Hindus believe the waters of the holy rivers Ganga, Yamuna and the mythical, invisible Saraswati, which meet at Prayagraj have the power to absolve them of sin.