Both Ethiopia and hosts Uganda won their opening games at the East and Central African championship, the Cecafa Senior Challenge Cup, in Kampala on Saturday.
In the first Group A game of the day Ethiopia, who are heading to the Africa Cup of Nations finals in South Africa in January, edged out newcomers South Sudan 1-0.
Striker Yonathan Kebede scored in the 60th minute with a clever tap-in after the South Sudan defence was caught off-guard.
Captain Leon Khamis had the two best chances for South Sudan, who were playing just their second ever international match after their 1-1 draw in a friendly against Uganda in July.
Assistant coach Seyoum Kebede, who is in charge of Ethiopia at the tournament rather than Sewnet Bishaw, admitted his side would have to improve.
"It is good to win the opening match in such a tournament, but we need to improve," he said.
With Issa Hayatou, the president of the Confederation of African Football, looking on Uganda began the defence of their title by dominating arch-rivals Kenya.
Vietnam-based Geoffrey Kizito eventually headed home the winner with 16 minutes remaining. The goal came shortly after Cranes goalkeeper Abel Dhaira had been rushed away in an ambulance following a collision with a Kenyan player.
The next Group A games are on Tuesday with Ethiopia taking on Uganda while Kenya face South Sudan.
Group B kicks off on Sunday with Burundi playing Somalia and Tanzania against Sudan.