Thousands of revellers from all over the world packed into Pamplona's main square to mark the start of the famous bull running festival. The San Fermin festival kicked off with the traditional midday launching of a firework rocket — known as the Chupinazo — from Pamplona's town hall balcony, decked out with the Spanish and Basque flags.

Pamplona 2017 San Fermin Chupinazo
Wine and sangria-soaked revellers celebrate the launch of this year's San Fermin festivalMiguel Riopa/AFP

The crowd in the square below raised their hands and screamed "Viva San Fermin!" as a marching band made its way though the middle of the throng. This was the signal for the revellers to start dousing each other in red wine and sangria. Those lucky enough to occupy the balconies around the square threw buckets of water or more red wine on to the crowd below.

The square was filled with people waving red neckerchiefs and wearing the festival's traditional outfit of white shirts and trousers, though they did not stay white for long once the sangria started spraying.

Pamplona 2017 San Fermin Chupinazo
The Chupinazo rocket is fired from the Pamplona town hall to mark the start of the San Fermin festivalCesar Manso/AFP
Pamplona 2017 San Fermin Chupinazo
The wine flows as the festival beginsCesar Manso/AFP
Pamplona 2017 San Fermin
A reveller catches wine poured from a balcony in PamplonaPablo Blazquez Dominguez/Getty Images
Pamplona 2017 San Fermin
Wine-soaked revellers pose during the opening day of the 2017 San Fermin festival in PamplonaPablo Blazquez Dominguez/Getty Images
Pamplona San Fermin 2017
A red-and-white sea of revellers soak each other with wine in a packed Pamplona squareMiguel Riopa/AFP
Pamplona 2017 San Fermin Chupinazo
The Pamplonesa band performs in front of the city's town hallAnder Gillenea/AFP
Pamplona 2017 San Fermin Chupinazo
The municipal band performs in front of the Town Hall of Pamplona during the launch of the 'Chupinazo'Ander Gillenea/AFP
Pamplona 2017 San Fermin Chupinazo
The municipal band plays at the town square during the start of the San Fermin festival in PamplonaSusana Vera/Reuters
Pamplona 2017 San Fermin Chupinazo
Revellers pour wine into another's mouth as the festival beginsCesar Manso/AFP
Pamplona 2017 San Fermin
A man drinks wine out of shoe at the start of the festival in PamplonaEloy Alonso/Reuters
Pamplona 2017 San Fermin
Revellers cool off with water thrown from a balcony in PamplonaEloy Alonso/Reuters
Pamplona 2017 San Fermin
Revellers cool off with water thrown from a balcony in PamplonaEloy Alonso/Reuters
Pamplona 2017 San Fermin
Revellers embrace as the 2017 San Fermin festival in Pamplona kicks offEloy Alonso/Reuters
Pamplona 2017 San Fermin
A reveller catches wine thrown from a balconyPablo Blazquez Dominguez/Getty Images
Pamplona 2017 San Fermin Chupinazo
Revellers hold up traditional red scarves during the start of the San Fermin festival in PamplonaSusana Vera/Reuters
Pamplona 2017 San Fermin Chupinazo
Revellers hold up traditional red scarves during the start of the San Fermin festivalSusana Vera/Reuters
Pamplona 2017 San Fermin Chupinazo
Participants celebrate the 'Chupinazo' (start rocket) marking the kick-off of the San Fermin festivalAnder Gillenea/AFP
Pamplona San Fermin 2017
Two revellers celebrate the launch of the San Fermin FestivalMiguel Riopa/AFP
Pamplona 2017 San Fermin
A reveller jumps from a fountain at Navarreria Street in PamplonaPablo Blazquez Dominguez/Getty Images
Pamplona 2017 San Fermin
A reveller jumps from a fountain at Navarreria Street as people enjoy the atmospherePablo Blazquez Dominguez/Getty Images
Pamplona 2017 San Fermin
Revellers enjoy the atmosphere during the opening day of the famous festivalPablo Blazquez Dominguez/Getty Images
Pamplona 2017 San Fermin Chupinazo
Pamplona 2017 San Fermin Chupinazo
Revellers hold up traditional red scarves during the start of the San Fermin festival in PamplonaSusana Vera/Reuters
Pamplona 2017 San Fermin Chupinazo
A naked reveller is thrown into the air during the official launch of the San Fermin festivalAnders Gillenea/AFP
Pamplona San Fermin 2017
Revellers cool off with water thrown from a balcony during the start of the San Fermin festival in PamplonaSusana Vera/Reuters
Pamplona 2017 San Fermin Chupinazo
Revellers hold an Ikurrina (Basque flag) at the start of the San Fermin festivalSusana Vera/Reuters
Pamplona San Fermin 2017
A street vendor wears hats in traditional colours on the first day of the San Fermin festival in PamplonaVincent West/Reuters

The Chupinazo is held a day before the first of eight bull runs. Thousands of people at the festival test their speed and bravery by racing ahead of six fighting bulls along an 850m course from a holding pen to the city's bull ring. The bulls are then killed by matadors in bullfights each afternoon.

The nine-day fiesta was immortalised in Ernest Hemingway's 1926 novel, The Sun Also Rises, and attracts thousands of foreign tourists. Dozens of people are injured each year in the runs, most of them in falls.