The Liverpool forward's two goals put Egypt four points clear with one match left in the preliminary campaign.
Salah had given his side a 63rd minute lead even though Egypt still looked tentative in a tense match with opponents who had yet to win a match at the bottom of the group.
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A defensive blunder had let him in, to the relief of the home crowd, but Egypt's dreams threatened to turn into a nightmare when Arnold Bouka Moutou equalised, firing past 44-year-old goalkeeper Essam Al Hadary with three minutes left.
The home side, though, won a 95th minute penalty which Salah converted to secure the trip to Russia – Egypt's first appearance at the finals since 1990 in Italy.
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