The 26-year-old midfielder fell to the ground without any contact with another player in the 70th minute of the game against Viitorul, just seven minutes after coming on as a substitute.
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 Batineanu told journalists.
Fans of the Bucharest club gathered outside the hospital late into the night to express their grief at the player’s death.
Club executive director Ionel Danciulescu expressed his shock after a death which recalled that of another club player Catalin Haldan who died playing a friendly in October 2000.
“I can’t believe it. It’s a nightmare. For me, for the team and for all Dinamo supporters. It’s too much,” said Danciulescu. “It’s as if we are cursed.”
Before arriving in Romania, Ekeng played for several European clubs, spending four seasons with French Ligue 2 side Le Mans from 2009 to 2013.
The player from Yaounde then transferred to Lausanne in Switzerland from 2013-2014 and Spanish side Córdoba from 2014-2015 before joing Dinamo.
“We will love you forever, Patrick Ekeng!” the Bucharest club wrote on Facebook, adding the player had “gone to a better world wearing the white-red shirt to join Catalin Haldan and other players who have written the history” of the club.
Ekeng made his debut for Cameroon in January 2015 and was named in the squad for the 2015 Africa Cup of Nations from which Indomitable Lions’ were eliminated in the group stage. He also played with the Cameroon U-20 team at the Africa Cup of Nations in Rwanda.
His death also echoed that of his countryman Marc-Vivien Foe, who died of a heart attack in 2003 playing an Confederations Cup match against Colombia at the Gerland Stadium in Lyon, France.
More recently defender Gregory Mertens died three days after suffering a heart attack playing for his Belgian side Lokeren in April 2015.
Cameroon international midfielder and captain Stephane Mbia tweeted his shock.
“Our cameroon football family has lost a brother. I cannot believe this. Condolences to his family. RIP Patrick Ekeng.”
Spanish club Cordoba also tweeted: “There are no words to express our sorrow over the death of Patrick Ekeng. We mourn your loss. We will never forget you friend. RIP.”
The Spanish La Liga also took to Twitter to express their condolences alongside a photo of the player in his Cordoba shirt, who last season played in the first division.
“La Liga expresses its regret at the death of Patrick Ekeng and sends its condolences to his loved ones.”