Mane, who also scored last Wednesday when Senegal beat Guinea-Bissau 2-0 at home, netted with eight minutes remaining to ensure they maintained their 100 percent record in Group I where they are guaranteed a top-two finish and therefore a place at the finals in Cameroon in January 2022.
Senegal have 12 points from four games, six ahead of second-placed Congo and nine ahead of Guinea Bissau in the third spot.
Senegal were runners-up at the last Cup of Nations tournament in Egypt in 2019.
Mane’s Liverpool teammate Naby Keita scored for Guinea as they stayed top in Group A with a 1-1 draw away in Chad.
Ahmat Abdaraman equalised just before halftime for Chad, who collected their first point after three successive defeats.
The tiny Comoros Islands boosted their hopes of a first-ever qualification as they beat Kenya 2-1 in Moroni to go top of Group G.
After drawing in Nairobi last week, the Indian Ocean islanders set off frenzied celebrations as El Fardou Ben Mohamed and Faiz Mattoir scored to ensure a famous win, which puts them on the cusp of a place in the finals.
Earlier on Sunday, Saidi Ntibazonkiza scored twice and Youssouf Ndayishimiye added the other as Burundi beat Mauritania 3-1 in Bujumbura. Burundi is one point behind second-placed Mauritania in Group E with both countries left with two qualifiers to play in March.
The top two teams in each of the 12 qualifying groups advance to the finals except in Group F where the highest finisher besides Cameroon, already in the finals as hosts but also playing in the preliminaries, goes through.