Angola beat Botswana 1-0 on Friday thanks to a soft Wilson Eduardo goal to join 14 teams who had already qualified for the 2019 Africa Cup of Nations in Egypt.
The remaining nine places will be filled on Saturday and Sunday with defending champions Cameroon among those hoping to make it to the biennial African showpiece.
Needing a win to be sure of finishing above Burkina Faso in Group I and joining first-time qualifiers Mauritania, Angola succeeded through a 21st-minute goal in Francistown.
The ball rebounded off the crossbar to Braga’s Eduardo, whose weak shot eluded three defenders en route to the net.
Floodlight failure delayed the second half by 30 minutes and Angola survived a few anxious moments before celebrating an eighth qualification for the Cup of Nations.
The furthest the oil-rich southern Africa country has gone in the tournament is the quarter-finals in 2008 and 2010, when they were hosts.
Burkina Faso edged Mauritania 1-0 in Ouagadougou through a first-half goal from Bertrand Traore, but had to settle for third place.
Angola and Mauritania finished with 12 points each from six matches, Burkina Faso 10 and Botswana one.
Nigeria are 143 places above the Seychelles in the world rankings, but needed a last-minute Moses Simon goal to seal a 3-1 home win in a Group E dead-rubber.
After Odion Ighalo converted a penalty for the Super Eagles, Rody Melanie equalised before half-time when goalkeeper Francis Uzoho fumbled a free-kick in Asaba.
Henry Onyekuru put Nigeria ahead again on 50 minutes, punishing slack marking to nod a cross into the net.
But despite an overwhelming superiority in possession, the home team had to wait a further 40 minutes before substitute Simon beat goalkeeper Ian Han Kong at his near post.
Winning assured Nigeria of first place in the group and South Africa will also go to Egypt provided they avoid defeat away to Libya Sunday.
Morocco and Tunisia, north African countries who have each won the Cup of Nations once, sealed first place in other groups through contrasting results.
The woodwork denied Morocco several times as they drew 0-0 away to already-eliminated Malawi in a Group B game marred by some spectators flinging missiles onto the pitch.
Tunisia trounced eSwatini (formerly Swaziland) 4-0 in a Group J match that marked the debut of 1980s France midfield star Alain Giresse as coach.
Syam Ben Youssef, Anice Badri, Naim Sliti and Yassine Meriah netted for the Carthage Eagles, who cannot be overtaken even if second-place Egypt win in Niger Saturday.
Emilio Nsue (twice), Pablo Ganet and Pedro Obiang — all born in Spain — scored for Equatorial Guinea in a 4-1 Group A romp away to Sudan with only pride at stake.