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.

Held every 12 years, the Maha Kumbh Mela or Great Pitcher Festival, as the religious event in the city of Prayagraj in the northern state of Uttar Pradesh is called, attracts more than 400 million visitors, both Indians and tourists.