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.

Several devotees are feared dead and many injured following a stampede in the early hours of Wednesday at Akhara Marg, close to the Triveni Sangam ghat at the Maha Kumbh Mela in Prayagraj.