The Moroccan national team scored at the edge of the first half with a free-kick goal from Hakim Ziyech but it was disallowed for offside.
The first half ended in a goalless draw at Doha's Al Thumama stadium.
Sabiri scored the opener with a superb precision-guided free-kick from outside the penalty area in the 73rd minute.
In stoppage time, Zakaria Aboukhlal made a close-range finish with an assist by Ziyech as the game ended with a 2-0 result in favor of Morocco.
Following two group matches, Morocco increased their points to four while Belgium collected three points after two matches.
It was Morocco’s first World Cup win in 24 years. Their last World Cup win was against Scotland 3-0 in France in 1998.
Source: Anadolu Agency