Hundreds of thousands of pilgrims, led by naked, ash-covered holy men, streamed into the sacred river Ganges yesterday at the start of the world's biggest religious festival.

The Kumbh Mela in the Indian town of Allahabad will see up to 100 million Hindus gather over the next 55 days to take a ritual bath in the holy waters, believed to cleanse sins and bestow blessings.

Before daybreak yesterday, a day chosen by astrologers as auspicious, hundreds of gurus, some brandishing swords and tridents, ran into the swirling and freezing waters for the first bath, signalling the start of events.

Assorted dreadlocked holy men, seers and self-proclaimed saints from all over the country have assembled for the colourful and chaotic spectacle, which offers a rare glimpse of the dizzying range of Indian spiritualism.

Mokshanand, a heavily bearded guru who emerged from the water in a small pair of saffron-coloured underpants, said: "I am ecstatic. When I enter the Ganges I feel so happy, it's a feeling I can't explain."

A naga sadhu, one of a devout, permanently naked sect of followers of the Hindu god Shiva, said: "Our biggest wish is that there is peace and that people should look after each other."

For most ordinary Indians, the Kumbh Mela is a religious holiday enjoyed in an almost carnival atmosphere, where prayers and blessings are offered and sought alongside family or friends camping together at the vast festival site.

The hardships of being squeezed in vast crowds, enduring endless whistling and barked orders from thousands of policemen and even catching a cold in the chilly weather are seen as a price worth paying for a dip.

Mayank Pandey, 35, a computer science professor, said: "You feel somewhat connected to somebody who is there above, and that's what it's all about."

The Kumbh Mela takes place every 12 years in Allahabad in Uttar Pradesh, with smaller but similar events every three years in other locations around India.

It has its origins in Hindu mythology, which tells how a few drops of the nectar of immortality fell on the four places that host the festival, Allahabad, Nasik, Ujjain and Haridwar.

For men like Ram Krishna Verma, 42, a farmer from the state of Chhattisgarh, who has travelled 700 kilometres, it is a time of solemn duty. He has come to scatter the ashes of his late mother. "She died two months ago," he said. "This is the final resting place."

The "Mother Ganges" is worshipped as a goddess. Most devotees dunk their heads under the water, some drink it and others bottle it and take it home as gifts.

Police expected 250,000 people yesterday with 20 million anticipated on February 15, the most auspicious day. Overall, organisers are counting on about 100 million coming, the same number as in 2001.

Organisers have set up 35,000 toilets, 14 medical centres, 22,000 street lights, 150 kilometres of temporary roads, 18 bridges, and new sewage facilities. Nearly 7,000 buses, as well as hundreds of special trains are expected to ferry people to and from Allahabad, where the heavily polluted Yamuna river flows into the equally dirty Ganges.