The stampede broke out on Sunday afternoon at the Nzerekore city during the final of a local soccer tournament between the Labe and Nzerekore teams in honour of Guinea's military leader, Mamadi Doumbouya, Guinea's Prime Minister Amadou Oury Bah said on the X platform.
"During the stampede, victims were recorded," Bah said, without being specific about the number of those killed.
The regional authorities were working to restore calm in the area, he said.
A coalition of political parties known as the National Alliance for Alternation and Democracy said the stampede resulted in dozens of deaths and injuries.
Local media reported that security forces tried to use tear gas to restore calm after the chaos that followed a disputed penalty.
"(The disputed penalty) angered supporters who threw stones. This is how the security services used tear gas," the local Media Guinea reported.
It said several of those killed were children while some of the injured being treated at a regional hospital are in critical condition.
Videos that appeared to be from the scene showed a section of the stadium shouting and protesting the refereeing before the clashes broke out as fans poured onto the field.
People were running as they tried to escape from the stadium, many of them jumping the high fence.
The National Alliance for Alternation and Democracy coalition called for an investigation.
It said the tournament was organised to drum support for the "illegal and inappropriate" political ambition of the military leader.
Guinea has been led by the military since soldiers ousted President Alpha Conde in 2021.
It is one of a growing number of West African countries, including Mali, Niger and Burkina Faso, where the military has taken power and delayed a return to civilian rule.
Doumbouya overran the president three years ago, saying he was preventing the country from slipping into chaos and chastised the previous government for broken promises.
He has, however, been criticised for not meeting the expectations that he raised.
