Nigerian officials on Thursday sought to allay fears about the health of President Muhammadu Buhari after his absence from the last two cabinet meetings.
Buhari's spokesman Garba Shehu said there was "no need for apprehension" that he had missed the meetings but he was only following medical advice.
"As eager as he is to be up and about, the president's doctors have advised on his taking things slowly, as he fully recovers from the long period of treatment in the United Kingdom some weeks ago," Shehu said in an emailed statement.
"Full recovery is sometimes a slow process, requiring periods of rest and relaxation," he said, adding that Buhari was still in charge, despite his lack of public appearances.
The president, who has spent most of his time at his private residence, talked regularly with Vice-President Yemi Osinbajo and received daily briefings on government activities, he said.
Buhari's aides repeatedly insisted the 74-year-old was "hale and hearty" throughout his time in London, where he spent nearly two months before returning to Nigeria in early March.
After arriving in Abuja, the former military ruler contradicted those assertions by saying he "couldn't recall being so sick" and revealing he had had blood transfusions and other tests.
Shehu's references to a "long period of treatment", convalescence and recuperation indicates a more serious condition than stated, although exactly what has not been specified.
The presidency said in January that Buhari's trip to London was for "routine medical check-ups" during a short holiday.
He was said to have been treated for a persistent inner ear infection during a previous trip last June.
Buhari dismissed claims during the 2015 presidential election that he was seriously ill with prostate cancer, saying it was an opposition smear designed to show him unfit to be head of state.
The health of Nigeria's president has been a sensitive issue since the death in office in 2010 of Umaru Musa Yar'Adua, which saw months of political turmoil.