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 what is being touted as the world’s largest religious gathering.

India's Maha Kumbh Mela, or Great Pitcher Festival, is set to be the world's largest gathering of humanity, with 400 million visitors expected at the six-week event that began this week in the northern city of Prayagraj.

Scores of naked Hindu ascetics smeared in holy ash charged into the water of holy rivers in northern India yesterday, dreadlocks flying, during the first “royal bath” of the Maha Kumbh Mela, or Great Pitcher Festival.