At least five people were taken to hospital as half-tonne fighting bulls knocked over thrill-seekers Thursday in the first bull run since 2019 at Spain's San Fermin festival in Pamplona.

No one was gored but several daredevils were trampled or knocked to the cobblestone pavement of the medieval northern city in the first of the festival's eight early-morning bull runs.

Of those taken to hospital, one was treated for a leg injury, while another suffered a knock to the head while falling and a teenager sustained an arm injury, a Red Cross spokesman said.

Six bulls guided by six tame steers that keep the herd together cleared a path through a sea of hundreds of runners mostly dressed in traditional white outfits with red neck-scarves.

The bulls raced along the roughly 850-meter course from a holding pen to the city's bull ring in 2 minutes and 35 seconds.

They will be killed in bullfights later Thursday.

"The bulls kept themselves in a tight pack, they steamrolled right through, so it was over very quickly," said Gordon MacDonald, a 46-year-old IT worker from Glasgow who took part in the run.

"It was a long time since we ran here so everybody was a bit kind of nervous, we couldn't remember exactly how it was going to go," he told AFP.

People from around the world flock to the city of around 200,000 residents to test their bravery and enjoy the festival's mix of round-the-clock parties, religious processions and concerts.

The annual festival, made famous by Ernest Hemingway's 1926 novel "The Sun Also Rises," was last held in 2019.

Officials called off the hugely popular event in 2020 and 2021 because of the COVID-19 pandemic, the first time the festival had been canceled since Spain's 1936-1939 civil war.

Sixteen people have died in the bull runs since 1910. The last death occurred in 2009.