Running with the bulls: San Fermin kicks off in Spain's Pamplona

Tens of thousands of revellers packed the main square in Pamplona's, northern Spain, on Sunday to celebrate the traditional “chupinazo” firework blast that marks the start of the San Fermin bull-running festival.

Nearly everyone, including the throngs of foreign tourists who come to the event, was dressed in the traditional garb of white trousers and shirt with red sash and neckerchief.

They sang. They shouted. And they drank alcohol with abandon.

As the rocket that starts the official party was fired off, many doused each other with red or sparkling wine.

The highlight of the controversial nine-day festival is the early morning “encierros”, or bull runs, starting on Monday, when thousands of brave or foolhardy souls sprint to avoid six bulls charging along a winding cobblestoned route to the city's bullring.

While gorings are not rare, many more people suffer contusions from falls as spectators watch from balconies and wooden barricades set up along the course. The spectacle is televised nationally.

The rest of each day is for eating, drinking, dancing and cultural entertainment, including bull fights where the animals that run in the morning are slain by professional matadors each afternoon.

The festival was made internationally famous by Ernest Hemingway's classic 1926 novel “The Sun Also Rises” about American bohemians wasting away in Europe.