Partygoers and bull-running fans packed the main square in Pamplona on Saturday to cheer the launch of a firecracker which marks the start of the northern Spanish city’s annual San Fermin festival.

Decked out in white T-shirts and trousers stained pink by wine, the crowd danced and waved traditional red handkerchiefs bearing the image of the local patron saint, Fermin.

The “chupinazo” rocket fizzed into the sky at midday, officially opening festivities during which specially bred bulls chase runners through an 800-metre stretch of narrow streets each morning at 8am.

Festivalgoers hold up kerchiefs as fireworks explode and confetti comes down in the Town Hall square. Photograph: Jim Hollander/EPA

More than 1 million people attend the nine-day festival each year, bringing a hefty contribution to the local economy.

One of several bull-running events in Spain, the festival regularly ignites debate about the treatment of animals.

Protesters with fake spears protruding from their backs took to the streets on Friday to highlight what they see as animal cruelty.

The city’s fiesta has also become one of the frontlines in the battle for social and legal change in Spain. Three years ago an 18-year-old woman was raped by five men – and a decade before a young nurse, Nagore Laffage, was beaten to death by a man with whom she had refused to have sex.

Last year the city authorities launched an app that allowed people who had been assaulted – or who had witnessed one – to report the incident to police headquarters in real-time.

• This article was amended on 8 July 2019 to change “sexually assaulted” in the penultimate paragraph to “raped”.