The 26-year-old defensive midfielder fell to the ground without any contact with another player just seven minutes after coming on as a substitute during the league game against Viitorul Constanta yesterday.
Ekeng, who joined the Romanian club in January, was rushed to hospital where staff were unable to resuscitate him.
"Resuscitation attempts were made for an hour and half without success," Dinamo team doctor Liviu Paltinean told journalists.