Hillary Andersson reports from Oshogbo

The Oshun festival has become the central pillar of the traditional religion of one of Nigeria's main ethnic groups, the Yoruba.

The week long ceremony is a celebration of the Orisha religion which is as old as Africa itself.

Festival has grown massively in recent years

During the climax of the festival, men and boys beat off the evil spirits which followers of Orisha believe are everywhere.

A virgin specially selected by the gods carries sacred objects down to the river Oshun which the goddess of water is believed to inhabit.

Crowds process after her, praying intensely, believing that on this day the gods will grant favours.

At the riverside, a sacrifice of flowers and other offerings is made to the goddess.

Among the crowds, the frenzy of praying reaches a peak. Women beg for health, prosperity and more children.

Austrian high priestess

At the heart of this revival is an 83-year-old Austrian artist, Susanne Wenger, a high priestess of Orisha herself.

Susanne Wenger: "One has to address oneself to another totality"

The rooms she lives in are as intriguing as her beliefs. Her house, her art and her life have become absorbed with the mysteries of the ancient gods.

"It is just what I am and what I feel. It is a kind of language. One does not live singularly. One does always have to address oneself to another totality," she says.

Susanne Wenger left Austria almost 50 years ago with a European who also enjoyed her love of African culture.

But eventually they parted and she remarried a traditional Nigerian drummer who drummed up the spirits of her faith.

Secret gardens

At the centre of the festival is the sacred Oshogbo forest, turned into a gallery of ritual art by Susanne Wenger during the past decades.

Sacred forest is full of statues representing gods

Without her art, the forest - the town's church to Orisha - may well have been built over and lost forever, like so many others in Nigeria.

The remarkable statues and shrines in the forest each represent one of the many gods of Orisha.

Susanne Wenger calls the statues a refuge for homeless gods who have been abandoned by modern society.

Because the place is crowded by homeless gods, she says, the spirits in the forest are strong.

Controversial religion

Orisha is a controversial religion in modern times: good gods are worshipped along with the violent ones.

One statue, for example represents the god commonly known as the god of smallpox.

Good gods are worshipped along with the violent ones

Susanne Wenger says that by Orisha custom children who have caught the disease should not take western medicine but instead pay ritual tribute to the god.

If they die, no-one is allowed to cry.

The BBC correspondent in Nigeria, Hillary Andersson, says the festival in Oshogbo has grown massively over recent years - at a time when the Orisha religion is under threat from scientific scepticism about spiritual matters.