Junior Kabananga capitalised on a goalkeeping error from Munir to give 10-man DR Congo a 1-0 win over Morocco in their opening game of the Africa Cup of Nations.
DR Congo had impressed in the 2015 edition of the competition, progressing to the semi-finals in Equatorial Guinea and beating the hosts on penalties to finish third.
Florent Ibenge's men have been drawn in a tough group as they bid to go one step further this time around, with holders Ivory Coast and Togo playing out a goalless draw earlier on Monday.
But DR Congo will go into the second round of fixtures at the top of the Group C after Munir's moment of misfortune handed them all three points.
Munir failed to deal with Firmin Ndombe Mubele's cross from the left, with Kabananga pouncing to turn home what proved the decisive goal.
Substitute Joyce Lomalisa Mutambala was sent off in the 81st minute for two bookings in quick succession and DR Congo were forced to play some of the closing stages with nine men due to an injury to captain Gabriel Zakuani, who did return for stoppage time.
But Morocco could not find an equaliser and DR Congo will now look to cement a place in the quarter-finals when they face Ivory Coast on Friday.
Only the crossbar prevented Morocco from taking the lead inside two minutes as Mbark Boussoufa curled against the woodwork from the edge of the area.
Defender Manuel da Costa then headed over from Mehdi Carcela-Gonzalez's free-kick before defender Chancel Mbemba had DR Congo's best chance of the half, his effort from just outside the box flying narrowly wide.
But DR Congo were gifted the lead 10 minutes after the restart.
Mubele got to the byline and whipped in a seemingly aimless left-wing cross, but Munir allowed the ball to creep under him and strike his near post, Kabananga making no mistake in volleying in the rebound.
Carcela-Gonzalez went close at the other end, firing an effort just past the right-hand post and DR Congo's hopes of preserving their advantage suffered a blow when Fabrice N'Sakala was taken off on a stretcher and replaced by Mutambala.
Youssef En-Nesyri's long-range strike was unconvincingly saved by Ley Matampi as Morocco continued to press for an equaliser, with the substitute then lashing over from close range at the far post moments later.
Mutambala was given his marching orders for a rash foul on Faycal Fajr having previously been booked for time wasting, and Youssef El-Arabi almost immediately took advantage, turning a point-blank header agonisingly wide.
Matampi produced heroics to deny El-Arabi three minutes from time and Morocco could not fashion another chance as DR Congo clung on.