At least four people were injured Saturday, including a man who was gored in the leg, during the first bull run of Pamplona's San Fermin festival in northern Spain, officials said.

Three people suffered bruises or cuts to their legs or back in spills, and all four injured runners were being treated in hospital, an emergency services spokesman said.

"None of the injuries are serious," he said.

No other details on the injured were immediately available.

Six half-tonne fighting bulls and six steers charged through the narrow, winding streets of the northern Spanish city, clearing a path through a sea of runners mostly dressed in white with red handkerchiefs.

The pack stampeded through an 850-metre (2,800-foot) course from a holding pen to the city's bull ring in just two minutes, 53 seconds.

During the final stretch a bull knocked a runner to the ground, and one of its horns speared the collar of the man's shirt. The animal then dragged him for several metres into the bull ring.

Every year between 200 and 300 participants in the week of bull runs are injured, around three percent seriously. Most are hurt after falling, but some are trampled or gored by the bulls despite increased safety measures.

The last death occurred three years ago when a bull gored a 27-year-old Spaniard to death, piercing his neck, heart and lungs with its horns in front of hordes of tourists.

The San Fermin festival, which features concerts, folk dancing, religious processions and round-the-clock street drinking in addition to the early-morning bull runs and evening bullfights, wraps up on July 14.