Youssef En-Nesyri’s towering header late in the first half gave first-time quarterfinalists Morocco a 1-0 lead over Portugal at halftime on Saturday.
En-Nesyri, who had twice headed over the crossbar earlier, leapt higher than both Portugal goalkeeper Diogo Costa and defender Ruben Dias to put Morocco ahead in the 42nd minute.
Portugal forward Joao Felix came close to opening the scoring on two occasions, forcing Morocco goalkeeper Yassine Bounou into an early save before his strike in the 31st minute took a deflection and narrowly missed the target.
The winner of the match will face either France or England, who play later on Saturday night, in the semifinal.
Ranked 22nd in the world by Fifa, Morocco has already beaten high-ranking Belgium and Spain in a tournament marked by upsets, causing wild celebrations by its fans.
Hundreds of Moroccan fans have flown into Doha for the match after Royal Air Maroc laid on seven extra flights, joining a large contingent already present in Qatar, where many Moroccans live and work. Fans were queuing for stadium access hours before the game.
With the Qatar World Cup the first to be held in an Arab country, Morocco has backed by fans from Iraq to Algeria who cheered its progress into the knockout stages.
By SuperSport