LAGOS (Reuters) - The haunting stone sculptures have stretched bodies with enlarged heads, mask-like faces and elongated chests - the kind of sharp, geometric qualities that inspired the works of Pablo Picasso and the Cubist movement in the 1920s.

Displayed at a Lagos gallery alongside colorful paintings of domestic scenes, they represent a revival of ancient art forms in Nigeria, rooted in traditional spirituality, that Christian missionaries tried to banish a century ago.

That revival coincides with a turn by the country's super rich elite and small but growing middle class towards art as a store of wealth.

An art investment boom is under way across emerging markets, but it has been seen as largely centred on China, India and Gulf Arab countries. The planet's poorest continent is still widely viewed in art circles more as a source of fine art for auctions in the developed world rather than a market in itself.

That may be slowly changing. Artist and designer Nike Davies-Okundaye sees growing interest by local as well as foreign collectors in the Nigerian art in her four-storey Lagos gallery, part of which is given over to traditional work: wood carvings of priests and stone statues of Yoruba deities.

A growing number of wealthy Nigerians are adding such pieces to their collections. Yet for many Christian or Muslim Nigerians, traditional African art, because of its link with animist religion, is still viewed as taboo - an invitation to dangerous black magic or idolatry.

That is a hurdle for artists trying resurrect their suppressed culture. But local interest in art is growing.

Lagos-based accountant Jumoke Ogun used to think of art just as something nice to hang on the wall, but that changed when her sister bought a painting as an investment.

"So now I no longer just dive in. I go away, try to find out more about the artist, how much their other works sold for," she told Reuters, standing in a Lagos gallery near a canvas of a classic Nigerian scene: women cooking street food at dusk.

Oscar Onyema, chief executive of Nigeria's stock exchange, has a very small but growing portion of the exchange's portfolio in Nigerian art, about 20 million naira ($122,400) so far.

"People are now using art as an alternative to other asset classes. We think this is a wise thing to do," he said. "We certainly expect that our own collection at the exchange will increase in value."

PETRODOLLARS AND PAINTINGS

Nigerian auctioneer Yemisi Shyllon - whose own collection is valued at roughly 5 billion Nigerian naira ($30.61 million) - says there was virtually no domestic art market in 2008.

Since then, around 775 million naira worth of art has sold at auctions, according to data he has gathered, and maybe three times that in galleries or private sales, he says.

That sum, while no more than a single work might fetch in New York, is significant for a country whose domestic art market is just beginning.

Nigeria's more than 160 million population, position as the continent's top oil producer and potentially huge middle class have proved a constant draw for luxury goods sellers.

Some Nigerian artists, like Bruce Onobrakpeya, have made it big internationally in recent decades, but in the past four years their works are also increasingly being bought at home.

Shyllon fits the global mould of the eccentric collector, with a garden featuring bronze or wrought iron sculptures, ornately trimmed hedges and peacocks, porcupines and crested cranes imported from east Africa.

"Southern Africa and east Africa are still ahead of our region when it comes to producing internationally recognised art, but Nigerians are becoming Africa's biggest collectors of art," he said, in a room crammed with realist paintings, totem poles and carvings of gods of fire, fertility or water.

Incongruously, he also has a Jesus statue, which he says he got because devout friends kept questioning all his "fetish" sculptures. "They were wondering where I stood on religion," he said, adding that he prefers not to have to make the choice.

SACRED TRADITIONS

Regardless of faith, many of Nigeria's top artists, even stylistically modern ones, are influenced by sacred traditions, especially those of the Yoruba ethnic group predominant in the southwest and the main city of Lagos.

Before European colonisers turned up, the many kingdoms and chieftaincies that now make up Nigeria had a proud tradition of art, such as wood or stone sculpture and tie-dying fabrics.

Like most art, it was rooted in religion, so when the pious 19th century British dismissed local carvings of Yoruba gods as idolatrous savagery, it nearly killed Nigeria's art scene. They destroyed hundreds of works; others, they carted off to museums.

"We're still recovering from the damage. To propagate their gospel, they told us ours was Satanic, and even now Christian Nigerians will say these traditional statues are demonic," said Reuben Okundaye, Nike's husband and art gallery manager.

Islam arrived in Nigeria many centuries before Christianity, but its effect on traditional culture was similar, if not as devastating.

Yoruba religion, with its gods and kings, has spread far beyond West Africa. Slaves brought it over the Atlantic to Latin America, where it is still practiced in forms such as Cuba's Santeria faith, blending Yoruba deities with Catholicism.

But in Nigeria, where Yorubas are now roughly 50-50 Muslim and Christian, mosques and churches both frown on animist religion.

The rise of U.S.-style Pentecostal churches has done the most damage, say Yoruba revivalists, because their allure lies in being "born again", in breaking with your past.

"It's a reason there is still big resistance to our traditional culture and arts," Shyllon said. Most only buy Western-style art, he said, but added that "the fact that now art is money is our best hope of revival."

OFFERINGS TO THE GODS

Before Christianity, most Yoruba villages had sacred groves dotted with shrines, sculptures and other art works representing gods, sacred animals and people. Few survived the arrival of Europeans.

But in the 1950s, a group of Nigerian artists and Austrian painter Susan Wenger revived the shrines in the Osun Osogbo forest, adding to the sculptures and restoring others in one of southwest Nigeria's last remaining dots of rainforest.

The grove is now a UNESCO world heritage site. Wenger stayed on in the adjacent town of Osogbo, becoming a Yoruba high priestess, until her death in 2009.

At an annual festival in the grove last month, thousands gathered by a river believed to be the earthly manifestation of Osun, goddess of fertility.

At the water's edge stood a giant stone statue of her, with angular arms outstretched, fixed to the root of a gnarly tree.

Women left offerings of yams, hoping to be blessed with a child, while figures in psychedelic robes called "Egungun" or masquerades, their faces covered, danced to beating drums.

In Yoruba folklore, Osun transformed herself into a river out of despair after her angry husband Sango, the axe-wielding deity of thunder who bears a striking resemblance to the Norse god Thor, stormed out.

Osogbo artists use materials and themes from such stories. Nike Davies-Okundaye, herself an understudy of Wenger, uses dyed cloth and makes mosaics out of myriad tiny beads.

Her works are kaleidoscopically coloured, recalling the bright masquerades that scare children at Yoruba festivals.

"For a long time we were praying 'God, please bring the oyibo (white man), because they were the only ones buying our art," she said, "But we see that's slowly changing now."

($1 = 163.3500 naira) (Editing by Pascal Fletcher and Philippa Fletcher)