Pamplona: Two Americans were gored and several other people were injured on Saturday during the second running of the bulls at this year's San Fermin festival in the northern Spanish city of Pamplona, officials said.

The regional government of Navarra said that a 22-year-old American man identified with the initials J.C. was in serious condition at a nearby hospital after being gored. Another 35-year-old American identified as B.H. was in stable condition after being gored.

Televised images showed a bull thrusting its horn into a man's buttocks before flipping him into the street, while another man's arm was impaled and he was dragged for several metres before the bull flung him off and stormed over him.

Three other Americans, two Frenchmen and three Spaniards - all men - needed treatment at the hospital for injures received during the frantic and crowded run of thrill-seekers.

On Friday, two Americans and a Spaniard were gored on the first running. All three were treated for non-life-threatening injuries.

The first part of Saturday's run was particularly dangerous, with the bulls plowing into the slower-moving crowds, knocking many runners down as they maneuvered through the narrow streets and wooden barricades.

The bulls from the ranch of Jose Escolar confirmed their reputation as being unpredictable. The bulls completed the 850-metre cobbled-street course in just over four minutes - well over the average of three minutes - because one bull broke away from the rest and turned around.

The lone bull had to be guided through the course by a small group of castrated bulls trained to accompany rogue bulls to the bullring, where they will face almost certain death later in a bullfight.

This was the third consecutive annual appearance by bulls from the Jose Escolar ranch, and the third that one of the six bulls has separated from the pack.

The nine-day San Fermin fiesta attracts tens of thousands of partygoers from Spain and abroad. It was popularized by Nobel Literature laureate Ernest Hemingway's 1926 novel The Sun Also Rises.