Mane netted the opening goal for Senegal in their Group H clash in Dakar after a tidy combination of passes in the 56th minute followed by a volley from Paris Saint-Germain defender Abdou Diallo, making his competitive debut for Senegal after switching his allegiance from France, for whom he played at under-21 level.
Egypt, who went to the last World Cup in Russia in 2018, had to do without Mohamed Salah due to the refusal of English clubs to release players to travel to countries on the British government's COVID-19 red list because of the 10-day quarantine they would face on their return.
Without him, Egypt turned in a feeble performance against Angola in Cairo but still won 1-0 after Magdi Asha converted an early penalty.
Gabon, with Pierre-Emerick Aubameyang back in the line-up, went ahead early but Libya fought back and snatched a last- minute winner from Sanad Al Warfali.
The qualifiers began earlier on Wednesday in Cameroon where the Central African Republic hosted their Group C qualifier against the Cape Verde Islands because their own stadiums were declared unfit for international matches by the Confederation of African Football.
Cape Verde went ahead through Julio Tavares in the driving rain but a mistake by their goalkeeper Vozinha allowed Tresor Toropite to equalise in the 53rd minute.
There are seven more African qualifiers on Thursday, including African champions Algeria at home to minnows Djibouti while Morocco, who qualified for Russia 2018, host Sudan.