Tens of thousands of revellers packed Pamplona this week to kick off Spain's best-known fiesta, the San Fermin bull-running festival.
Spaniards and foreigners jammed into the main Plaza del Ayuntamiento to hear the traditional shout from a City Hall balcony: 'Viva San Fermin'.
Seconds later a firecracker, known as the 'chupinazo', detonated, setting off celebrations among a mass of people dressed in white with red handkerchiefs.
The frenzy marked the start of a nine-day festival charged with alcohol and laced with danger.
The most courageous, or inebriated, of the revellers are drawn by the daily thrill of being chased through the northern city's streets from a pack of huge, charging bulls.
It is a combination expected to draw more than a million tourists to Pamplona, popularised worldwide by Ernest Hemingway's 1926 novel, The Sun Also Rises.
'I'm here to have fun, to enjoy with the locals and to run with the bulls,' said 24-year-old Australian Adam Espron.
Two large glasses of sangria in his hands, Californian tourist David Panijelene was euphoric. 'It is the first time for me. Today is my birthday,' he said.
The festival's first bull run was held at 8am (0600 GMT) today, when hundreds of people raced ahead of six fighting bulls and six steers stampeding through an 848.6-metre course from a holding pen to the city's bull ring.
The bull run takes on average just under four minutes, with 2,000 to 3,500 runners daring to get as close as possible without being trampled or pierced by the beasts' horns.
Every year between 200 and 300 participants are injured. Most are hurt after falling, but some are trampled or gored by the bulls despite increased safety measures.
The most recent death occurred two years ago when a bull gored a 27-year-old Spaniard to death, piercing his neck, heart and lungs with its horns in front of the hordes of tourists.
This year organisers have launched a free iPhone app in English to help revellers to assess the chances that they will emerge from the festival unharmed.
It asks users about their behaviour at the festival, including how much they have had to drink and how many hours of sleep they have received.
The daily bull runs are the highlight of the festival, which ends 14 July, but there is also dancing and drinking.
In the evening the beasts are killed in the bull ring and their meat is served up in city restaurants.
The city of some 200,000 residents expects the number of people who will take part in the festival to be at least 1.5m this year.
The official opening of the festival and the morning bull runs are broadcast live on public television, drawing millions of viewers.
