Those hurt fell as they were chased by six rampaging bulls through the narrow streets of Pamplona on the second day of the city's nine-day fiesta.
None was gored but a 56-year-old man was taken to hospital after fracturing his left sinus, hospital officials said.
One man aged 66 suffered severe concussion while three others had minor injuries in a huge scrum of hundreds of people who joined the early-morning fray to see if they could outrun six bulls over 800 metres (900 yards).
Also today, police said they have made five arrests after a woman said she had been sexually assaulted overnight, a police spokesman told AFP.
Also Read
The nationality of the suspects was not clear but a protest march against the assault was planned for today evening.
Ahead of the fiesta, a tradition dating back to medieval times, Pamplona city hall had launched a campaign urging a "safe" environment for women "without sexist aggression".
Last month's general election saw an animal rights party win a record number of votes in Spain as nearly 285,000 people cast their ballot for PACMA -- or 1.2 per cent of all votes.
PACMA bitterly opposes "cruel" Spanish traditions involving animals, including bullfighting, and persuaded authorities in the Spanish northern region of Castilla y Leon to ban the killing of bulls during traditional festivals, particularly the famed Toro de la Vega bull run.