The government's reluctance to say anything about Mr Buhari's medical status has helped fuel rumours about the president's condition. "Else, Nigerians will have to wait for memoirs in years to come, when the nation would have moved on".
His absence prompted intense speculation in the country about the President's health and many false reports circulated online saying he had died.
Some rumors identify Jibril as a Chadian replacement for the Nigerian president. "I will soon celebrate my 76th birthday and I will still go strong", said Buhari during a town hall meeting in Poland.
Buhari said Monday at the UN Climate Change conference in Poland that no country can fight climate change on its own and called for global support to save the receding Lake Chad and ensure its safety from Boko Haram fighters.
George H.W. Bush lies in state in Washington
His death also reduces membership in the exclusive ex-presidents' club to four: Jimmy Carter, Bill Clinton, George W. Bush attends a ceremony to unveil a new garden named in his wife's honor, Sept 29, 2011, in Kennebunkport, Maine.
President Muhammadu Buhari on Sunday promised that he will no longer complain about the problems his administration met on ground at the inception of the current administration. "It's [the] real me; I assure you", Buhari added.
Rumours about his demise spread across Nigeria a year ago, when the president spent five months on medical leave in London to treat an undisclosed illness. In April, he wrote on Twitter: "Buhari is dead and he never came back from London".
Deadly attacks against the Nigerian military are on the rise.
The president commended Nigerians in Poland for maintaining good relationships with their host communities despite such cases of hostilities and racial discrimination.
In his remarks, the Ambassador of Nigeria to Poland, Mr Eric Adagogo Bell-Gam, praised Nigerians living in Poland for being worthy ambassadors of the country.