Four people including one Australian has been injured on the first day of the Running of Bulls in Pamplona, Spain.
A 24-year-old man, identified with the initials J.C is being treated for trauma at the Navarra hospital complex.
A hospital spokesperson said the Australian man was diagnosed with a head injury but was released at 11am local time with the medical forecast recorded as "slight".
At 8am on Sunday, thousands of people dressed in white except for a red neck handkerchief and red scarf tied around their waist, ran through the streets in one of the most important traditions of the annual San Fermin fiesta.
Australian traveller Connor travelled from Wollongong to run the streets.
"We've been watching Youtube clips all morning so we're all good."
With a gun shot, six bulls and three steers chased revellers down the street which were heavily controlled by police.
Along the 848m route, the mass crowd caused dangerous pileups as people tried to get out of the way.
From 5am, hundreds of people started to find their spot along wooden fences that lined the street.
Aitor Zuasti, 22, who ran his first encierro when he was 16, says the bull run is the most important part of San Fermin as it dates back to medieval times when bulls would be transported through the city to the bullring.
He runs with his father, Jokin who has taken part in the encierro for the last 40 years.
Jokin Zuasti first ran with the bulls at the age of 13.
"I've been running since I was a child and it's something I carry inside me," said Jokin Zuasti.
"The most important is to be physically fit, have good reflexes, don't be nervous and stay calm."
While there was one visible protest hanging from a balcony condemning the bull running, Jokin Zuasti said he wanted to tell the international community that they respect the bulls during the encierro.
"The bull ring is different. In the arena we see them as not having hearts."
Hundreds of people get injured each year and according to festival organisers, 14 people have died durig the running since 1922.
The last person gored to death was a Spaniard in 2009.
According to fiesta organisers, over one million people from around the world are expected to visit Pamplona over the two-week festival which concludes on July 14.