Police say at least 30 people were killed and many more injured in a stampede at the world's largest religious gathering as millions of pilgrims rushed to dip in sacred waters during the Maha Kumbh festival in northern India.

At least seven people were killed and dozens suffered injuries in a stampede at the Maha Kumbh Mela in India, where millions have gathered to bathe at the confluence of three sacred rivers.

Hindu devotees and mystics have gathered in the northern Indian city of Prayagraj for the Maha Kumbh festival, which is the largest religious congregation on Earth.

People were trampled as pilgrims at the Maha Kumbh Mela, one of the world’s biggest gatherings, gathered where the Ganges and Yamuna Rivers meet.

The Hindu festival that turned deadly in northern India on Wednesday is a religious gathering with deep spiritual meaning for devotees who come by the millions to take a cleansing dip in waters they consider sacred.

Millions of devout Hindus thronged the northern Indian city of Prayagraj on Thursday for the Maha Kumbh festival, a day after dozens died in a stampede on the most auspicious day of the six-week event.