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 were killed and over 30 have been injured in a stampede at the Maha Kumbh Mela, one of the world's biggest gatherings that occurs every 12 years.

Indian authorities have ordered a probe into the stampede at the Maha Kumbh Mela Hindu festival that killed dozens of devotees on Wednesday as millions gathered for a "holy dip" in sacred river waters as part of the six-week event,