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.

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.

At least 30 people have been killed in a crush at the world's largest religious gathering, the Hindu festival Kumbh Mela in northern India, officials say. The incident took place early on Wednesday when devotees on the riverbanks in the city of Prayagraj were trampled by other pilgrims rushing to take part in a sacred day of ritual bathing.