The 26-year-old snapped the lower part of his left leg landing badly while competing in the vault in the men’s qualifying at the Rio Olympic Arena. The French delegation later confirmed he had suffered a double tibia and fibula fracture.
Ait Said fell to the mat in agony clutching the back of his knee and the lower part of his leg, which visibly flopped to one side to gasps of horror from the crowd.
He was treated by medical staff for several minutes before being stretchered off to applause from the crowd.
“We’re still overcome by emotion, it’s unexpected, dramatic,” French national team director Corinne Callon told AFP.
“I am proud of the team, there were still three rotations and they did well to finish, they managed to regroup and now they’re overcome.”
It is the second Olympic blow for the gymnast from Antibes who missed the London Games because of a knee injury.
Fellow gymnasts were visibly shocked.
“I was warming up when I saw it on TV,” said Germany’s Fabien Hambuechen, a silver medallist from London 2012 on the horizonal bar.
The German team were also reeling after national all-around champion Andreas Toba was forced out earlier with a knee injury.
“There’s always more difficult, higher risk. It’s getting dangerous,” said Hambuechen.
“I don’t like this new system. I’m the guy who still loves the 10.0. It was a simple system. It was more flexible for everyone. The new system is pushing people and making it dangerous.”
American Danell Leyva, the 2012 Olympic all-around bronze medallist, added: “I heard other gymnasts say ‘don’t look, don’t look.
“Even though we’re on different teams we know each other and I’ve known Samir since I was 14. It really sucks, but we have a job to do.”
Rings specialist Aït-Said, a former European champion, was France’s leading medal hope on the rings apparatus in Rio.
He had been third overall on rings with a score of 15.533 in early qualifying behind world champion Eleftherios Petrounias of Greece (15.833) and Olympic champion Arthur Zanetti of Brazil. Zanetti also scored 15.533 but had a higher execution mark than the French gymnast.
Toba suffered a cruciate ligament injury to his right knee during his execution of the floor routine.
The 25-year-old was helped off, but continued on the pommel horse, before hobbling off.
The perfect 10.0 scoring system was revamped after a scoring controversy at the 2004 Athens Games gymnasts have since been awarded points starting at an initial 10-point score. Gymnasts are also given scores based on the difficulty of their routine.