Ethiopian’s Abiy Ahmed and Sudan’s Gen Abdel-Fattah al-Burhan met early this week in Port Sudan, in a bid to vouch for peace, dialogue to end the war.
Harare will host the 44th SADC Summit on August 17, where President Mnangagwa will take over as chairperson of the bloc.
It is legal in Cameroon to extend the mandate of lawmakers.
Biya, 91, is one of Africa's longest-serving presidents. He took over in 1982.
A hand grenade exploded close to his sleeping quarters, South Africa's military said.