A fight broke out between fans of rivals US Ouakam and Stadede Mbour and police fired teargas to break it up.
The resulting confusion triggered the stampede, Sports Minister Matar Ba told Reuters by telephone.
Deadly stampedes at soccer matches have been common in Africa, where safety standards are low.
At least 17 people died and scores were injured in a stampede in a match in Angola in February, when hundreds of supporters stormed the stadium.
– By REUTERS