Hindu ascetics known as Naga sadhus, many naked apart from a coating of ash and carrying swords or tridents, led the bathers at the Kumbh Mela, or pitcher festival, in the northern town of Haridwar.
Most devotees started gathering at the river banks packed with crowd in the wee hours of Thursday and by 9 a.m. (GMT 0330) a police official said 2.2 million people had already taken a holy dip since yesterday.
All participants at this year's event, that runs until the end of April, are required to present a negative coronavirus test result before being allowed into the festival grounds, authorities said. But there was little evidence of social distancing in place on Thursday
as bathers jostled at the riverbank.