Libya beat former gold medallists Nigeria 2-0 on Wednesday in the first leg of a 2020 Tokyo Olympic Games second round qualifier.
Montenegro-based Zakaria Alharaish netted twice in a match moved from Libya to Ben Guerdane in neighbouring Tunisia for security reasons.
Nigeria suffered a major blow just before halftime when goalkeeper Adamu Abubakar was sent off for handling outside the box.
The teams meet again on Monday in Asaba with Nigeria, the 1996 Olympic champions, seeking to avoid a shock early exit.
Olympic qualifiers are restricted to under-23 footballers with three over-age players permitted at recent finals.
Elsewhere, the Democratic Republic of Congo built a 2-0 home lead over Morocco in Kinshasa thanks to Jackson Muleka.
The striker from the top Congolese club, TP Mazembe, put the home side ahead just before halftime and netted again midway through the second half.
DR Congo have never qualified for an Olympics football tournament while Morocco have achieved the feat seven times, most recently for the 2012 London Games.
Sudan were another country to build a 2-0 first-leg lead at home, against highly rated Kenya in Omdurman, with in-form Waleed Bakhet bagging a brace.
Guinea edged Senegal 2-1 in a showdown between western African neighbours with Morlaye Sylla snatching the winning goal three minutes into the second half in Conakry, while Zambia look set to secure a place among the qualifiers for the third round during June after building a 1-0 lead away to Malawi in Blantyre.
There were two 0-0 draws, between Burundi and Congo Brazzaville in Bujumbura and surprise qualifiers South Sudan and Tunisia in Juba.
Africa has been allocated three places for Tokyo and Cameroon, winners of the gold in Sydney in 2000, are already through to the third round after Sierra Leone were disqualified.