Sharp-horned fighting bulls thundered through the slippery, cobbled streets of Pamplona on Monday, skewering one daredevil in a fast, adrenaline-charged opening run of Spain’s San Fermin festival.

Thousands of white-clad runners with red scarves opened a path for the five half-tonne charging bulls and six steers, man and beast occasionally sliding over on the glistening cobbles of the overcast northern city.

The animals tore along a winding 848.6-metre course in just two minutes and 25 seconds, injuring five runners.

A bull gored one 52-year-old Spaniard in the groin area but his injury was not considered serious, the region’s health authorities said. Another four men were taken to hospital for various unspecified injuries and 37 people were treated at the scene.

“We were standing in the alley way waiting for the bulls to come and everyone started jumping,” said 26-year-old Texan oil company worker Mathew Whitman.

“Then they just came very fast,” he said.  “It was just like a big rush of people that came and pushed us and we were trying to run, and we were pushed against the wall and they went past,” he added. “Kind of scary yes, but it was very cool.”

Fellow runner 32-year-old Canadian Collin Goyman said the run was much faster than he had anticipated.

“So many people, more than I expected, it was crazy,” he said.

 “I didn’t think that the bulls would run that fast.” A firework launched the first race of the San Fermin festival, a heady nine-day mix of partying and adrenaline-chasing, which draws hundreds of thousands of people from around the world.

Tens of thousands of spectators looked on, many peering from overhanging balconies, as runners fled the charging animals, some daring to touch the sides of the beasts.

“I was scared but it was great,” said 25-year-old first-time runner Francisco Jose Guiterrez Aguilera, on holiday from the southern city of Seville.  “I did not manage to touch them, no, but I got very close.”

In the inaugural run, only five of the usual six fighting bulls took part because one of the mostly black-and-white mottled animals had injured a leg the previous day.

The festival in this city of 200,000 residents was made famous by Ernest Hemingway’s 1926 novel “The Sun Also Rises”.

The bull runs are believed to have started when butchers began running ahead of the beasts they were bringing from the countryside to the San Fermin festival.

Last year, 50 people were taken to hospital during the festival’s eight runs, including 23 revellers caught in a bloody human pile-up on the final day of the fiesta.

Several hundred more were treated for minor injuries at the scene.

Most injuries are not caused by bull horns but by runners falling, or being knocked over or trampled by the animals.

Fifteen people have been killed in the bull runs since records started in 1911.

The most recent death took place five years ago when a bull gored a 27-year-old Spaniard in the neck, heart and lungs.

Pamplona city hall has this year introduced fines of up to 60,000 euros ($82,000) for those who violate rules intended to minimise the risk of the bull runs.

Using a camera during a bull run or taking part while drunk are among the acts prohibited under a new city ordinance.