Ighalo volleyed in his second just past the hour and he then turned provider to play in Iwobi to steer home three minutes later
The great rivals have met six times in the biennial tournament, including three finals that Cameroon won, one after a penalty shootout.
The Senegalese star struck on 15 minutes with a close-range shot after a passing move carved open the Ugandan defence in Cairo
The squirrels of Benin have reached an AFCON quarter final for the first time
Senegalese Mane and Ugandan Onyango were included in the 2018 African team of the year chosen by a Confederation of African Football (CAF) panel.
Cameroon will meet Nigeria in a clash of continental giants in the last 16
Excitement has been building in the country as the team emerged on top of group B after beating three-time tournament winners Nigeria 2-0
The qualification of Senegal raised to 12 the number of teams who have secured places in the second round
Charges were brought in May after a government investigation into alleged graft at the body
The Indian Ocean islanders will advance as winners of Group B ahead of Nigeria