An American tourist and two Spaniards were gored by bulls during a bull run on the sixth day of the San Fermin festival in Pamplona on Friday.
The American was in a "serious" condition as was one of the Spaniards. The other was described as having "less serious" injuries.
A further four bull-runners were injured, including another American. All those injured were men; few women take part in the run.
The gorings were the first this year at the festival which started on Sunday. The bull run is held at 8am each day and usually lasts between two and five minutes.
The animals taking part are later killed by matadors in the bull ring.
The San Fermin festival in Pamplona was made famous by the novel The Sun Also Rises by Ernest Hemingway.
Most runners dress in white with red kerchiefs tied around their neck.
A man from Madrid was the last person to be killed during a Pamplona bull run, after being gored in the neck in 2009. There have been 14 fatalities over the past century at the fiesta.