PAMPLONA, Spain — The start of the annual San Fermin bull-running festival was delayed briefly on Saturday by masked men who unfurled a huge Basque flag, blocking the view of a balcony where a rocket that officially marks the beginning of the revelry is launched.
Minutes before the celebrations were due to begin, several masked men were seen unfurling the flag, known as the Ikurrina, and draping it from rooftops after launching a cord across the square by using a fishing rod.
Thousands of revelers, dressed in traditional white with a red handkerchief around their necks, packed the square chanting "Viva San Fermin" as the flag was removed.
Scuffles broke out as youths shouted insults in the Basque language and made offensive gestures at the balcony where dignitaries also waited for the view to be cleared.
The rocket shot upwards to cheers, marking the official beginning of the celebrations, 19 minutes late.
A firework also exploded among the crowd, causing some alarm and confusion.
The nine-day fiesta — a heady mix of alcohol, daily bull runs, all-night partying and adrenaline — was immortalized in Ernest Hemingway's 1926 novel "The Sun Also Rises."
The first of eight bull runs will begin at 8 a.m. (0600 GMT) Sunday when thousands of thrill-seekers hope to outrun six fearsome bulls along a narrow 875 yards (800 meters) course through the city's streets.
Beasts and humans often fall over, jostling and stomping on each other as they hurtle down dew-moistened cobblestone alleys on their way towards the city's bullring.
Late in the afternoon the bulls will face matadors and be killed in the ring, with their meat served up in some of Pamplona's best restaurants.
Dozens of people are injured each year in the morning runs. Most get hurt after tripping and falling in the rush, but some are gored and trampled by the massive beasts.
The fighting bulls used in the centuries-old fiesta can weigh up to at 1,380 pounds (625 kilograms) and have killed 15 people since record-keeping began in 1924.