Tens of thousands of Hindus seeking absolution of their sins immersed themselves on Monday in freezing waters at the confluence of sacred rivers, as India began a six-week festival expected to draw the world's largest gathering of humanity.

Millions of Hindu devotees, mystics and holy men and women from all across India flocked to the northern city of Prayagraj on Monday to kickstart the Maha Kumbh festival, which is being touted as the world's largest religious gathering.

Authorities in India are racing against time to get the city of Prayagraj ready to host the Hindu festival Kumbh Mela, described as humanity's biggest gathering. About 400 million pilgrims are expected to attend the 45-day spectacle,

Maha Kumbh Mela or Great Pitcher Festival begins in India on Monday, a Hindu sacred event that will be the world's largest gathering of humanity as it showcases religion, spirituality, tourism and crowd management.

India set for Hindu festival Maha Kumbh Mela | REUTERS WARNING: May contain nudity The Maha Kumbh Mela, the world’s largest gathering of humanity, begins in the northern Indian city of Prayagraj, with millions of devout Hindus arriving to take a dip in the holy river Ganga.