WASHINGTON � The first picture of Nigerian President Muhammadu Buhari seen in 78 days -- since he left Abuja for medical treatment in Britain -- surfaced on Sunday: a photo that shows him smiling during a luncheon meeting in London with a delegation of state governors from Nigeria.

Buhari adviser Femi Adesina posted the photo on Facebook, along with an account of Sunday's meeting by Imu state Governor Rochas Okorocha. The governor, who along with others at the luncheon is a member of Buhari's All Progressives Conference party, wrote that the president was cheerful and attentive during a discussion that lasted more than an hour. There is no independent verification that the photo is authentic.

Including his current stay in Britain, which began on May 7, the 74-year-old president has been away from Nigeria for nearly two-thirds of this year - 128 days - seeking treatment for an illness that has never been described in detail. The lengthy absences have prompted concern, speculation and questions in Nigeria; periodic government statements about Buhari have been met with increasing skepticism.

Nevertheless, presidential adviser Adesina quoted Governor Okorocha as saying: "Nigerians don't have to worry at all. ... President Buhari will be back as soon as the doctors give him the green light."

In Buhari's absence, Vice President Yemi Osinbajo has been running the country as acting president. The president's prolonged absences have left many Nigerians wondering when Buhari will return, or even if he will return, and whether he is fit to lead the country.

The growing public skepticism was evident last month, when an audio recording of Buhari commemorating the end of Ramadan stoked suspicion and concern about his health. Some Nigerians questioned whether the voice they heard was Buhari's.

The infrequent updates and secrecy around Buhari's health have caused some to question whether he is even alive.

In his post Sunday, Adesina quoted Okorocha as saying: "The merchants of lies have been put out of business, and Nigerians will not buy the garbage they have been selling. All those who look up to fake news can find better use for their time."

The governor said Buhari was asked about the swirling rumors concerning his health, but laughed them off, "completely unperturbed by the cocktail of lies."

Buhari spent almost two months in Britain in January and February. On his return in March, he did not resume work immediately. In April and early May, Buhari was back in Nigeria, but he missed three cabinet meetings and was said to be "working from home." In early June, a month after he returned to Britain, the president's wife said he was "recuperating fast."

Buhari had been expected to address the nation at the end of May, the midpoint of his first presidential term, but that speech never took place.

Buhari is not the only African leader to spend extended time seeking medical treatment overseas this year. Angolan President Jose Eduardo Dos Santos and Zimbabwean President Robert Mugabe have spent extended time in Spain and Singapore, respectively, tending to health concerns.

Source: Voice of America