At least three people were gored during the first bull run at the annual San Fermin festival here on Sunday, local authorities said.
The incident, which took place in the city's old quarter, left six people wounded, including the three persons who were gored during the first bull run or 'encierro', CNN quoted a statement from Royal Navarre Hospital.
Two of the victims were identified as American nationals -- a 23-year-old man from Kentucky and a 46-year-old man from San Francisco. The third person was a 40-year-old man from La Rioja in northern Spain, according to the hospital.
Three other sustained injuries ranging from mild to serious, the hospital said.
The bull run tradition, dating back to centuries, commences every morning for eight days during San Fermin.
The festival, which draws thousands of people around the world, kicked off on Saturday in Pamplona in northern Spain with pomp and gaiety. It sees bullfights and people participating in parades and dancing to the tunes of classical Spsh music.
The festivities take place in honour of Saint Fermin, the patron saint of Pamplona.
"After launching two rockets, the bulls charge behind amateur daredevils -- many dressed in traditional white attire with dashes of red -- for 825 meters, which is the distance between the corral and the bull ring," the festival's website said.
The annual bull festival will go on till July 14.
This is not the first time that injuries have been reported during the San Fermin. Last year, nine people were wounded in the first two days of the festival.
( With inputs from ANI )