Turning the street corner to find an army of giant red ants tapping out drum rhythms, an eight-foot ogre and a merman riding chariots made from huge shells and carried by dolphins is an unlikely scenario by any stretch of the imagination.

But for two days a surreal fantasy land will take over the city for the 12th annual Streets of Brighton Festival.

International and local street performers are gathering for the extravaganza which coincides with the National Street Artists meeting, held at the University of Brighton's Sallis Benney Theatre.

They will amaze, confuse and amuse pedestrians who stumble on each of the inspirational and individual acts, all performed for free from 1pm to 5pm today and tomorrow.

The celebration, produced by Zap Art as part of the Brighton Festival, is funded by the Arts Council of England, the European Union, Brighton and Hove Arts Commissions and supported by the city council and Brighton University.

An eclectic mix of mime, dance, music, comedy, carnival and physical theatre, the Streets of Brighton has become one of the largest and most vibrant street arts festivals in the UK.

People dressed as giant prawns will kick cherry-tomato footballs, a human table football will burst into a performance of the Riverdance, a human letter will try to post himself into a human letter box while astronauts, mummified butlers and the Cornish Women's Institute Olympic squad wander the streets.

Veronica Stephens is a coordinator of the of programme - the non-commissioned aspect of the festival - and has been part of the Zap Art team for five years.

She said: "It has grown in popularity and recognition since it started. What I really enjoy is the fact that it is free and accessible. It opens up a wealth of opportunities for people who might not be able to access conventional theatre and performances.

"The performers do not get any fee for doing this and that makes it really special.

"Most of the acts are in the North Laine, it's the hub of everything and the roads are wide enough to fit everything in."

New Road, Church Street, Gardner Street, Jubilee Street and Pavilion Buildings will all be closed to traffic for the two days.

From yesterday the Dot Comedy team are transforming the Pavilion Gardens into a giant privet hedge maze for their production, Get Lost! Those who dare to enter the plastic privet will be greeted by curious characters including crusty gardeners and the Minotaur's wife.

One of the festival highlights is the UK premiere of Joueurs de Lumnieres by internationallyrenowned Groupe F, who were inspired by images of Earth as seen from above.

Led by artistic director Christophe Berthonneau, Groupe F is the company behind some of the most breathtaking pyrotechnic choreography of recent years including the opening and closing of the Olympic Games in Barcelona, the Eiffel Tower on the millennium and the closing of the 1998 World Cup at the Grand Stade de France.

The Argus reporter Kate Morrison got a sneak preview of what to expect at tomorrow evening's free performance at Preston Park when she saw the production in Paris last August.

She said: "It's not just a giant amazing firework show, it's more pyrotechnic theatre.

"You have to be prepared to sit and think about it while you are watching it rather than just being amazed by what's going on but it's also very beautiful.

"There are some amazing parts like a guy covered in fairy lights with flaming wings swooping across the stage and giant flame throwers sending up plumes of fire to heavy rock riffs.

"I thought it was about the end of the world and what man is doing to the world with global warming and climate change but apparently it's not as simple as that."

Mr Berthonneau said: "I have no words to describe this work. I'm trying to speak in a global language but on a human scale. It's about how somebody good with a good mind can still create something wrong and how the image of something wrong can be so beautiful. I wanted to leave people with the memory of at least five big images to take away with them."

Other large scale performances include Souterrain by WildWorks. Set in Stanmer Park, the story of Orpheus's quest into the Underworld to find his true love, Eurydice, is played out by a professional company alongside village residents and local school pupils.

Tomorrow, more than 200 amateur and professional singers from Brighton and Hove and the surrounding area will perform Imperfect Harmony, an uplifting musical celebration, at The Level at 5.15pm.

Ms Stephens, of Zap Art, added: "Street art has really moved on quite a bit. It's not just a bunch of fire eaters and jugglers. It covers all strands of the arts but it is under-funded and it's profile has never been so great as theatre or opera. We have a wealth of creative, talented people who are creating extraordinary high-quality work. Should they be given more funding I am sure the scale of their work would be as grand as that of any national opera or theatre."