Panic spread through the crowd at the match in the town of Uige between Santa Rita de Cassia and Recreativo de Libolo in Angola's domestic league season.
"There was a blockage at the entrance to the January 4 stadium... this obstruction caused multiple fatalities -- 17 deaths, and there are 56 injured in the hospital," police spokesman Orlando Bernardo told AFP.
He added that there were an unknown number of children among the dead, and that hospitals were treating those injured.
Police said hundreds of fans had tried to enter the already packed stadium to see the match, causing a crush that pushed some people to the ground.
Many of the dead were trampled to death or suffocated.
"While the players were on the field, outside fans were trying to get into the stadium and a gate probably gave way to the pressure of the crowd causing several people to fall who were literally trampled on by the crowd," said the Recreativo de Libolo club in a statement on its website.
"There are already 17 confirmed dead and at least 59 wounded... (this was) a tragedy without precedent in the history of Angolan football."