Critics of Nigerian President Muhammadu Buhari expressed anger after he flew to London for a medical visit, criticising his frequent trips abroad for treatment and the country's run-down health system.
Mr Buhari, 78, has made several trips to London since he came to power in 2015. He was re-elected for another four-year term in 2019.
Although the nature of his illness has never been made public, he said in one of the trips that he had "never been so ill" and that he had received several blood transfusions.
The presidency said the retired general, who was military ruler in the 1980s, would be away for two weeks.
"He is due back in the country during the second week of April," his office said.
The main opposition Peoples' Democratic Party condemned the trip, saying it was an indication that Nigeria's healthcare system had failed.
"It is indeed worrisome that under President Buhari, even the hitherto highly rated State House Clinic has become so moribund that it cannot provide a simple medical check-up for Mr President," the party said.
It said his frequent trips were a drain on the treasury.
"The PDP is disturbed that while Mr President jets out for medical treatment in well-equipped hospitals abroad, our hospitals and medical personnel are in very sorry situation while millions of our compatriots suffer," it said.
Local and social media were also full of outraged remarks by Nigerians over the trip.
The latest London visit came just hours before doctors in government hospitals threatened to strike over pay and inadequate facilities.
Mr Buhari's health became a subject of debate before the last election when the opposition claimed he was not physically fit to govern, but he won a second term.
His state of health became a sensitive subject in Nigeria after former leader Umaru Musa Yar'Adua died in 2010 and it emerged that his illness had been kept secret for months.