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, which is so large it can be seen from space.

Vast crowds of Hindu pilgrims in India began bathing in sacred waters on Monday as the Kumbh Mela festival opened, with organisers expecting 400 million people -- the largest gathering