The stampede occurred at the entrance to the Barea stadium on Friday where a crowd of about 50,000 spectators had arrived to attend the event, Al Jazeera reported.
“The provisional toll shows 12 dead and some 80 injured,” Madagascar’s Prime Minister Christian Ntsay told reporters at a hospital in Antananarivo.
The Indian Ocean Island Games are a multi-disciplinary competition being held in Madagascar through September 3.
They were created by the International Olympic Committee (IOC) in 1977, and include athletes from Mauritius, Seychelles, Comoros, Madagascar, Mayotte, Reunion and the Maldives.
Madagascar President Andry Rajoelina, who was present at the opening ceremony, called for a minute of silence.
“A tragic event occurred because there was pushing. There were injuries and deaths at the entrance,” he said in a televised speech.
TV broadcast showed dazed and shocked people trying to locate their shoes piled amongst objects lost in the deadly crush.
Other images from inside the stadium, shared on social media, showed the stands packed with spectators.
At least 15 people were killed in a similar incident at the Mahamasina stadium in 2019.