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,

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.