French long jumper Salim Sdiri was speared by a javelin in a freak accident at the Rome Golden League meeting on Friday.
Sdiri was hit by the javelin which had been launched by Finland's Tero Pitkamaki at the other side of the arena at the Olympic Stadium.
The 28-year-old Sdiri collapsed to the ground before being taken to hospital.
The men's javelin and long jump competitions were taking place at the same time when the accident happened.
Pitkamaki appeared to lose his footing as he launched the javelin which veered off course, landing in Sdiri's side.
When he saw what had happened, Pitkamaki held his head in his hands in shock.
"Sdiri had a 4cm injury in his right side," said Giuseppe Fischetto, one of the medics at the scene.
"The point of the javelin partially penetrated his side and he was taken to hospital. Now we will have to see if the pleural membrane was damaged or if it stopped just before the muscle," he said.