Abuja: Nigerian President Muhammadu Buhari needs further rest in Britain following medical tests but there is no need to worry about his health, his spokesman said on Tuesday, as his absence enters the second month while the oil producer is in recession.
Buhari, 74, left for London for medical leave a month ago for an unspecified illness, putting Vice President Yemi Osinbajo, 59, in charge.
He had originally planned to stay 10 days.
The government has sought to allay concerns of a void at the helm of Africa's biggest economy at a time that it is battling recession by stressing that Osinbajo has full powers as acting president.
"The president needs to rest for some further time," Buhari's spokesman Femi Adesina told reporters at the presidential villa in Abuja.
"From the results of the (medical) tests further rest has been recommended."
He declined to say when Buhari might be back or what his condition is, saying only: "There is no cause to worry. He is the one who owns his body. There is nobody who knows his body better than him."
Osinbajo, a commercial lawyer, has been holding cabinet meetings and continuing working on a economic reform plan needed to get a World Bank loan to help plug a deficit due to a collapse of oil revenues.
The central bank on Monday devalued the naira for retail customers, days after a top advisory body demanded at a meeting chaired by Osinbajo an urgent review.
Buhari has rejected a devaluation despite even some officials privately saying the high naira rate had been deterring badly needed investment.
Osinbajo, who comes from the southern port Lagos, has also travelled during Buhari's absence several times to the Niger Delta oil hub to discuss development projects to end attacks by militants fighting for oil revenues on pipelines.
He has travelled to other states and met anti-government protesters who had marched on the villa - in contrast to Buhari who did not travel much in recent months, talking mainly to his key aides in the villa coming, like him, from the army or Muslim north.
Buhari's predecessor, Goodluck Jonathan, was sworn in after the death in 2010 of president Umaru Yar'Adua.
His illness created a power vacuum that was only filled by Jonathan, his vice president, after three months of political infighting.