Tanzania continued their giant-killing run in the 2012 Olympic Games qualifiers with a 1-0 win over Nigeria.
Thomas Ulimwengu nodded a quick throw-in past goalkeeper Dele Ajiboye eight minutes from time to give the home side victory in Dar es Salaam.
Nigeria, who had scored 16 goals in four matches, squandered many chances.
Their coach Austin Eguavoen remains confident, promising to thump the East Africans in the second round second leg match in Abuja later this month.
But Tanzania coach Jamhuri Kihwelu remains hopeful of claiming another high-profile victim in the competition, having earlier seen off the challenge of 2000 Olympic gold medallists Cameroon.
South Africa, another team to impress this year, came unstuck in Benin and lost 3-1 after taking the lead on the half-hour mark through leading scorer Bongani 'Drogba' Ndulula.
The hosts responded as Fadel Suanon struck twice within three minutes before half-time and William Dassagate added a third early in the second half with a fierce drive.
It was a bad weekend for southern African teams as Zambia crashed 3-0 in Algeria where Sid Ahmed Aouadj scored in each half and Djamel Belamri got the other goal in first-half stoppage time.
Ivory Coast recovered impressively after falling behind in Brazzaville after just four minutes to defeat Congo 2-1 and take a significant step toward reaching December's mini-league final phase.
Ernest Maboto scored for the Congolese but Lacina Traore levelled and Cheick Toure snatched the winner for a team coached by former international Alain Gouamene.
A late Abderazak Hamdallah goal earned Morocco a 2-1 home win over the Democratic Republic of Congo while the Sudan-Egypt, Gabon-Mali and Tunisia-Senegal matches ended goalless.
The return legs will be played on the weekends of 17-19 June.
The eight teams who make it through will play in a final tournament, with two groups with four teams, in a country of one of the qualified teams in December.
Three of the sides will qualify for London 2012, with a fourth team playing off against an Asian side for another place at the Olympics.