Identified only by her initials J.E., a 23-year-old Australian woman was gored in the back during the last day of San Fermin's bull-running festival in Pamplona, Spain.

The woman was rushed to Navarra Hospital where she received immediate treatment for a damaged right lung and several fractured ribs. Doctors described her condition as being "very grave," said the regional government that organizes the festival.

The woman was struck by a massive Miura bull as she clung to wooden barriers outside the bullring entrance, regional health authority spokesman Javier Sesma said.

The woman's injuries come alongside four other goring incidents on Sunday, involving three Spaniards and one American. Two of the Spaniards were described as having "light" injuries, while the diagnosis for the other two runners had not yet been released, Reuters reports.

On Saturday, a 19-year-old Spaniard was left in a "very serious" condition after runners fell and piled up at the entrance to the bullring, where the run ends. Several people were trampled.

On Friday, three men were gored, including an American who had his spleen removed.

Over the past century, 14 people have died in the annual weeklong festival, which normally concludes with the bulls' slaughter in the bullfighting ring where the running ends.

The last person to die was a 27-year-old from Madrid gored in the neck by a bull in 2009.

The bull-running festival began in the 13th century, with the official annual celebration surrounding the running taking place each year after 1592. People are believed to have started running with the bulls sometime in the 1800s, with state regulation in San Fermin eventually coming in 1867.