The 24-year-old El Kaabi, who plays for Moroccan club Renaissance Berkane, was top scorer at this year’s African Nations Championship.
Boufal scored two goals this season in 26 Premier League games but has been struggling for playing time recently following a row with Southampton manager Mark Hughes.
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Striker Rachid Alioui, who has undergone surgery on a torn hamstring, also misses out.
Alioui has enjoyed a remarkable season with Nimes, helping the club gain promotion to the French top flight with 17 goals and four assists. He was injured last week.
A versatile midfielder now with Fenerbahce, Dirar was a key element of the Monaco side that won Ligue 1 last season. Belhanda also played in the French league for several seasons before joining Galatasaray last summer.
Morocco opens its World Cup campaign on June 15 against Iran. Portugal and Spain are also in its group.