A fire has torn through at least 18 temporary tents at a massive Hindu festival thronged by millions of people in India’s northern Prayagraj city.

Over about the next six weeks, Hindu pilgrims will gather at the confluence of three sacred rivers where they will take part in elaborate rituals.

Millions of pilgrims hoping to cleanse their sins by ritual baths at India's Kumbh Mela festival rely on key lavatory workers to clear up behind them -- those born on the lowest rung of the Hindu caste system.

It’s late evening in the city of Prayagraj and the roadside vendors selling snacks are packing up their wares to shut for the night.

The 'royal bath' is a key part of the event, held every 12 years in the city of Prayagraj in Uttar Pradesh, significant because Hindus believe it confers salvation from the cycle of birth and death, in addition to absolution of sins.

A large fire broke out at a Hindu religious festival, the Maha Kumbh Mela, in the northern Indian state of Uttar Pradesh on Sunday, but the blaze was quickly brought under control and no injuries were reported,