AKIPRESS.COM - Some four million people have taken to the waters at the confluence of the sacred Ganges and Yamuna rivers at the Kumbh Mela festival - humanity's largest gathering, BBC reports.

At least 15m people are expected on the first day alone. Officials project about 120m visitors over 49 days.

Hindus believe bathing at the rivers will cleanse their sins and bring salvation.

The holy men were among the first procession to arrive early Tuesday.

The Naga sadhus are the biggest draw of the festival - held in the northern city of Allahabad, recently renamed Prayagraj - and can be counted on to arrive in massive colourful processions.

At the last Kumbh in 2013, female ascetics were allowed to bathe at the confluence of the rivers - known as the Sangam - for the first time. A few hundred transgender people already bathed on Tuesday morning.