The blast of a traditional firework on Saturday opened nine days of uninterrupted partying in Pamplona's famed running of the bulls festival.

A member of the northern Spanish city's official brass band was chosen for this year's launch of the rocket, known as the "Chupinazo," to mark 100 years since the local ensemble's foundation.

The blast was met by an eruption of joy from revelers, who sprayed each other with wine, staining in pink the traditional attire of white clothes and a red scarf.

Early 20th-century American author Ernest Hemingway immortalized the fiesta in his "The Sun Also Rises" novel.

During the festival, Pamplona's population swells from around 200,000 residents to around a million visitors, who are attracted by the adrenaline boost of bull runs along an 850-meter (930-yard) street course to the city’s bullring and seamless nights of partying.

The protests of pro-animal rights groups have also become a fixture in recent years. On the eve of the festival, dozens of semi-naked activists staged a performance simulating speared bulls lying dead on Pamplona's cobbled streets to draw attention at what they see as animal cruelty for the sake of human entertainment. Bullfights are protected under the Spanish Constitution as part of the country's cultural heritage.