Alhaji Mahama died on Thursday after he suffered an acid attack from two assailants, who are in the grips of the police.
A funeral is currently ongoing at his family house, Akalbila House, where he has been laid in state.
Nana Addo cut short his tour of Europe after hearing news of the death of Alhaji Mahama, whom he describes as “a friend of mine”.
Thousands of mourners, our correspondent say, are at the funeral grounds to pay their last respects to the regional chairman.
TV3’s Rabiu Tanko Mohammed reports that conspicuously missing are NPP’s National Chairman Paul Afoko and General Secretary Kwabena Agyepong, against whom the crowd is wielding placards.