Mnangagwa ascended to power in November 2017 in a military coup.
A few weeks before that, Mugabe had fired him as relations between the two soured amid allegations that Mnangagwa, who at the time was the country's first vice-president, was plotting to unseat Mugabe through a military-backed faction in the ruling Zanu-PF party.
Mugabe turned 95 on February 24.
During his birthday celebrations with close family, the former strongman described Mnangagwa as a “cruel” man and called on him to remove the army from civilian matters.
Not much has been known about Mugabe’s movements until Mnangagwa revealed he was out of the country for medical treatment.
Since coming to power in November 2017 and subsequently winning a disputed poll on July 30 last year, Mnangagwa has been battling to save the economy from collapse.
The latest Freedom in the World Report on political rights and civil liberties by Freedom House says Zimbabwe has returned to a pre-coup situation.