Nigeria says President Muhammadu Buhari has extended his medical leave in London for a second time.
A statement Tuesday from adviser Femi Adesina says that during the president's annual checkup, "tests showed he needed a longer period of rest."
The statement said there is no reason for Nigerians to worry but did not say when Buhari, 74, will return.
The leader of Africa's most populous country left for London on January 19 and has been seen only in photographs since then.
He was originally scheduled to return February 5, but his office said that doctors advised him to stay in London to await the results of medical tests.
Aides to the president have refused to say what is ailing him, fueling speculation on social media about his condition.
Worry about a power vacuum has been limited because Buhari transferred authority to Vice President Yemi Osinbajo before his departure.
Nigeria experienced a near-constitutional crisis in 2009 when President Umaru Yar'Adua left the country for extended medical treatment and left no one in charge. The crisis led the Senate to grant full powers to Yar'Adua's deputy, future president Goodluck Jonathan.