Nigerian President Muhammadu Buhari returned to work on Monday after nearly two months' medical leave in Britain, the presidency said.
"President Muhammadu Buhari today resumed duties after his vacation," presidential spokesman Femi Adesina said in a statement.
Buhari, 74, who returned to Nigeria last Friday, hopes to end weeks of uncertainty about his health and fitness to lead.
In line with the constitution, he returned to work by sending a letter to the country's parliament.
During his absence, his office had repeatedly denied claims the leader was ill and insisted he was "hale and hearty".
But when he returned to Nigeria's capital of Abuja on Friday, a gaunt-looking Buhari said he "couldn't recall being so sick since I was a young man" and described receiving "blood transfusions".
He also said that despite feeling better, he still required rest and further treatment for his undisclosed sickness in the coming weeks.
Vice-President Yemi Osinbajo said he had an hour-long meeting with Buhari on Monday to "bring the president up to speed" on the state of the nation.
"He has given a few directives on what we should be doing on so many areas, the northeast, budget, the economy, a wide range of issues," Osinbajo told reporters after the meeting.
"His readiness for work is not in doubt at all. In fact he is over-ready."
Another presidential spokesman Garba Shehu said Buhari would take some time to ease back into his job after so long away, warning that there wouldn't be a "dramatic" return.
"He is coming out of an ailment and like he himself had said, he needs to start gradually," Shehu told Nigerian-owned Arise News television in an interview broadcast on Sunday.
Shehu said the date of Buhari's return to London for follow-up treatment was unclear and would only be determined by the president and his doctors.
Buhari had "no knowledge" of his illness before he left for London on January 19, he added.
The health of Nigeria's president has become a sensitive issue following the 2010 death of president Umaru Musa Yar'Adua from a long-standing, but secret, kidney complaint.
The presidency had been keen to avoid the impression of a political vacuum and Osinbajo has been a visible presence in the months Buhari has been away.
He was formally handed powers as acting president during Buhari's absence.
Buhari faces a tough task of rehabilitating Nigeria's sputtering economy, which contracted in 2016 for the first time in two decades, before the next general election due in February 2019.
But observers see his health as a key factor in the coming months, with the potential for it to create a bitter power struggle within his All Progressives Congress party.