In Group C on Sunday (AEDT), Nigeria put on an impressive display of attacking prowess but had to hang on for a narrow 3-2 win over Tunisia, becoming the second team to make sure of a place in the last 16.
Victor Osimhen opened the scoring a minute before halftime and captain Wilfred Ndidi and Ademola Lookman added two more after the break.
But Tunisia staged a late comeback with goals from defenders Montassar Talbi and Ali Abdi that set up a frenetic finish.
It was Nigeria's second win in Group C and ensures they will top the standings, even with one first-round fixture still to play.
Their six-point haul is three more than second-placed Tunisia with Tanzania and Uganda, who drew 1-1 in Rabat earlier, on one point each.
Against Senegal, Cedric Bakambu put the Congolese into the lead in the 61st minute but Mane equalised eight minutes later with his 51st goal for his country, one of the favourites to win the tournament.
The two countries both have four points from their opening two games and look set to progress comfortably into the last 16 with a final group game to come for each on Tuesday.
Senegal are ahead of DR Congo on goal difference in the standings after they beat Botswana 3-0 in their opening fixture on Monday while Congo edged past Benin 1-0 the same day.
Earlier, Yohan Roche scored a deflected winner as Benin claimed a first ever AFCON victory with a 1-0 Group D success against Botswana in Rabat.
Benin took the lead in the 28th minute when Roche played a one-two in the box with captain Steve Mounie and his shot from 10 yards took a wicked deflection off a defender and into the net.
Benin finally celebrated a victory at the continental finals at the 16th attempt following their debut in 2004, and despite the fact they were quarter-finalists in 2019. They also have five draws to go with 10 defeats.
Egypt on Friday became the first team into the last 16 when they beat South Africa 1-0 to make sure of top place in Group B.
