PAMPLONA, Spain -- Tens of thousands of revelers showered each other with sparkling wine and waved red kerchiefs as the blast of a small rocket signaled the start of this year's edition of the running of the bulls.

Spain's most famous summer festival kicked off Friday in the jam-packed main square of this northern town. People from around the world, many wearing the traditional red kerchief and white shirt and pants, roared their approval as an official on a balcony at city hall declared the San Fermin festival under way. He then lit the rocket and its echo boomed through the plaza.

The first of eight runs in which daredevils dash through the streets of Pamplona with six powerful fighting bulls begins Saturday.

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  • The music band plays after the 'Chupinazo', the official opening of the 2012 San Fermin fiestas, Friday, July 6, 2012 in Pamplona, Spain. Revelers from around the world kick off the San Fermin festival with a messy party in the Pamplona town square, one day before the first of eight days of the running of the bulls. (AP Photo/Daniel Ochoa de Olza)

  • Revelers partying during the 'Chupinazo', the official opening of the 2012 San Fermin fiestas, Friday, July 6, 2012 in Pamplona, Spain. Revelers from around the world kick off the San Fermin festival with a messy party in the Pamplona town square, one day before the first of eight days of the running of the bulls. (AP Photo/Daniel Ochoa de Olza)

  • A family pose in a cardboard poster painted with bulls announcing the famous San Fermin festival, in Pamplona northern Spain, Wednesday, July 4, 2012. On July 6, the San Fermin festival will begin with the ''txupinazo'' or opening ceremony with people participating in bull runs, music and dance, through the old streets of the city. (AP Photo/Alvaro Barrientos)

  • Revelers hold up traditional red neckties during the 'Chupinazo', the official opening of the 2012 San Fermin fiestas, Friday, July 6, 2012 in Pamplona, Spain. Revelers from around the world kick off the San Fermin festival with a messy party in the Pamplona town square, one day before the first of eight days of the running of the bulls. (AP Photo/Daniel Ochoa de Olza)