When a Masry defender failed to cut off a long free-kick from goalkeeper Benjamin Ochan, substitute Nsibambi scored with a volley in Kampala.
Young Africans of Tanzania were another club from the east of Africa to build a 1-0 lead at home over opponents from the north as they beat Mouloudia Alger of Algeria.
Wits of South Africa failed for a third time within two months to penetrate an Egyptian defence when held 0-0 by Smouha in Johannesburg.
The South Africans lost 1-0 overall to Al Ahly in the CAF Champions League last month and were demoted to the second-tier Confederation Cup.
Mounana of Gabon built a 2-1 lead over ASEC Mimosas of the Ivory Coast, whose hopes of overall success were enhanced when Fabius Dosso halved the deficit on 74 minutes.
Louis Autchanga scored midway through the opening half in Libreville and Nic Zamble doubled the advantage soon after half-time.
Njiva Rakotoharimalala salvaged a 1-1 draw for CNaPS Sport of Madagascar with a last-minute equaliser against Recreativo Libolo of Angola in Antananarivo.
Julsy Boukama-Kaya from Congo Brazzaville had given the visitors a mid-second half lead.
Highlight of 10 first legs Sunday is the clash between title-holders TP Mazembe of the Democratic Republic of Congo and JS Kabylie of Algeria.
Mazembe have won 10 CAF titles and Kabylie six, placing both clubs among the five most successful in pan-African competitions.
The play-offs pit Confederation Cup last-32 winners against Champions League last-32 losers with 16 group places at stake.