Blood-red streams of tomato juice oozed through the streets of the tiny Spanish town of Bunol as tens of thousands of people hurled tonnes of squashy fruit in the world's biggest food fight.

With a thundering firework at midday signalling the start of the "Tomatina", five trucks dumped 120 tonnes of plum tomatoes into Bunol's narrow central street where 35,000 people were expectantly awaiting the ammunition.

Locals and visitors from around the globe lobbed the tomatoes at each other and, when the fruit turned to puree, reached down to whisk red froth into the air. The "People's Square" filled with the acidic sweet smell of tomatoes and slimy stained bodies.

"We never do anything like this in Brisbane, we're all so controlled...It's insane," said an Australian visit.

"It's bonkers!" said Clare Fuchs from London. "I don't think I'll be having a Bloody Mary this afternoon."

Locals had draped plastic sheeting over their houses and some even boarded up windows but the town's white facades were still left spattered red.

Locals of Bunol -- with a population of 9,600 -- say the tradition started in the mid-1940s, under the authoritarian rule of General Francisco Franco. Goltran Zanon, 70, locally recognised as one of the founding fathers of the now world-famous event, says it all began with kids pitching tomatoes at balloons during a balloon-flying show.

Others say a group of youngsters started a food fight with their salad at lunchtime and it became a tradition.

The event -- the highlight of a week-long festival -- was banned for a short time when revellers pelted a government official and the town held a funeral for its favourite fruit.

"More than half the village showed up in mourning to bury an enormous tomato," Zanon said.

But Pilar Masmano, 80, says the festival -- which costs the town hall 36,000 euros -- is not what it was.

"It's just degenerate now," she said, adding that foreigners do not know how to throw a tomato as the locals do, squashing it first to ensure a satisfying splat rather than a painful thump.

Alisa from Japan agreed: "He hit me in the eyes...It was very painful."

As the fruity orgy wound down and the hoses came out to wash down the streets, die-hards made for the deepest pools of tomato and wallowed like pigs in mud.

(Agencies)