A senior police officer said at least 30 people died as a crowd panicked at the Hindu Kumbh Mela mega-festival in the northern city of Prayagraj.

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.

Moments before a deadly stampede at the world's biggest religious gathering in India, Hindu devotees queuing to take a spiritual bath in a river said they pleaded with police to open barricaded routes to thin out a surging crowd.