Story highlights It's the second time President Buhari has taken medical leave in 2017.

President Buhari has been battling an undisclosed illness.

(CNN) New pictures have emerged of Nigeria's ailing President Muhammadu Buhari for the first time since he left the country on medical leave 80 days ago.

President Buhari has been battling an undisclosed illness since the start of the year and has spent long periods out of the country receiving treatment in the UK.

On Sunday, his aides released a photo of the President having lunch with senior member of his ruling party, All Progressives Congress (APC) in London.

"The President sends his best wishes to all Nigerians. He will be back to Nigeria as soon as his doctors give the go-ahead," his office tweeted along with the picture of him at the lunch table.

There has been intense speculation in the country about the president's health with many false reports that he had died emerging online.

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