On Benin's national voodoo holiday, performers dressed as guardians of the night swirled in costumes resembling technicolour haystacks, delighting worshippers and tourists alike.

Over a thousand people gathered in the small Atlantic coast town of Ouidah on Tuesday, once an important port in the slave trade, to watch the elaborate annual rituals of dance and drumming to honour the 500-year-old religion's panoply of gods and spirits.

"They come in increasing numbers because voodoo is no longer considered sorcery, it is no longer considered barbarism," said voodoo spiritual leader Daagbo Hounon Houna II, adorned in colourful beads and a top hat.

Voodoo is practiced by around 12% of the West African country's population of 13 million people, but the authorities also want to use these deep spiritual roots and spectacular customs to attract more tourists and boost the agriculture-dependent economy.

In Ouidah, dance groups move to spellbound drumming and chants as spectators watched and shot videos on their phones.

Nigerian therapist Flora Domenis, 44, travelled to the festival with friends from the Caribbean, who she said had a special interest in these kind of traditions due to their shared African heritage.

"For them, there is a lot of interest in discovering the roots of our ancestors, the African roots," she said.

Spectator Jean Marie Ngondjibangangte from Cameroon was particularly impressed by the multi-coloured masks and female dancers' intricate footwork.

Voodoo "is extraordinary and we as Africans must do everything we can to promote this culture," he said.

As part of its development plan, the government has set aside a stretch of beachfront between the main city Cotonou and Ouidah as a special tourism zone for visitors, who it hopes will also be keen to visit historical slave sites, pre-colonial palaces, and tour the natural wonders of Benin's interior.

There is a way to go. Only around 350,000 tourists visited Benin in 2020, although numbers have been rising steadily since 292,000 visited in 2016, according to the most recent annual data from the World Tourism Organization.

French tourist Elodie Wine, 23, said seeing the group dances and fantastical costumes of the Ouidah festival was likely to be the highlight of her trip to Benin.

"It was beautiful. We didn't think there would be so many people here, but it's awesome to see," the trainee midwife said.