Two people died while trying to enter a stadium in the Angolan capital Luanda to see Pope Benedict XVI, Vatican spokesman Federico Lombardi told AFP.
"We don't have any details about the circumstances of the drama or the identity of the victims," he said on Saturday.
"The Holy Father will speak about this tragedy during a Mass he is due to hold on Sunday in Luanda," he added.
Portugal's LUSA news agency quoted senior police official Paulo de Almeida as saying that a young man and woman -- whose ages were not given -- died and 18 others were injured around noon local time (1630 IST) when the gates of the stadium opened.
The two died at the scene. Eight others were taken to the Josina Machel hospital with injuries.
Ten more were treated on the spot, Lusa said, adding that a criminal investigation had been launched.
More than 30,000 people had gathered at the stadium to hear the 81-year-old pope speak to youths in the former Portuguese colony ruined by a 27-year civil war.
More than half of Angola's population is under 18, and many bear physical scars of the decades of fighting that left the southern African country one of the most heavily landmined nations on the planet.
The pope is in Angola on the second and last leg tour of Africa, his first visit to the continent since taking over as pontiff.