President Ali Bongo of Gabon who has been in hospital since October has suffered a stroke.
Vice-President Pierre Claver Maganga Moussavou provided the first official details of his President's illness.
The 59-year-old leader left hospital in Morocco earlier this month and is recovering at a private residence in the capital Rabat after weeks of silence about his condition.
Moussavou said President Bongo had suffered a cerebrovascular accident or CVA, commonly known as a stroke.
"Nobody should rejoice over the death or illness of another, those who have never known a CVA, pray to God that they never know one," Mr Moussavou said in a speech in Franceville in the south of the country.
"I would not wish it on anyone, not even my worst enemy."
A lack of official news after President Bongo fell ill at an economic forum in Saudi Arabia on October 24 sparked speculation the Gabonese leader was incapacitated or even dead.
The vice-president was part of a delegation of high-ranking officials who visited President Bongo on Tuesday in Morocco, where he flew at the end of November after a stay in hospital in Riyadh.
A presidential spokesman had initially talked briefly of severe fatigue when referring to President Bongo's illness.
Official statements did not give details of his condition, though some sources had referred to a possible stroke.
The Bongo family has governed the oil-rich equatorial African nation for five decades and long maintained close ties with former colonial master France.
Diplomatic ties cooled after Ali Bongo was elected in 2009 following his father's death and French authorities launched a corruption investigation into the family's assets.
The President's spokesman Ike Ngouoni had said the president was in the Saudi capital for a flagship economic forum when he fell ill.
"The doctors who assessed him said he is suffering from severe fatigue due to extremely high levels of activity in recent months," he said.
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Bongo is feeling better and has been told to rest, Ngouoni added, while calling for "vigilance" against "fake news" following false reports of his death.
A Cameroon TV station had announced live on air on Saturday that the Gabon president had died, without providing any evidence, he said.
Bongo was scheduled to appear Wednesday on a panel at the Future Investment Initiative forum, but was not seen during the discussion.
Saudi Crown Prince Mohammed bin Salman visited him in Riyadh's King Faisal hospital that evening, the official Saudi Press Agency (SPA) said on Thursday.