Nigeria’s President Muhammadu Buhari will travel to London on Sunday night for follow-up consultations with doctors after a previous trip there earlier in 2017, a spokesperson said.

“Government will continue to function normally under the able leadership” of Vice-President Yemi Osinbajo, presidential spokesperson Femi Adesina said in an e-mailed statement. The duration of Buhari’s absence would be determined by doctors, Adesina said.

“The president wishes to assure all Nigerians that there is no cause for worry,” the spokesperson said.

Buhari delayed his departure by several hours on Sunday night to meet 82 Chibok girls freed by Boko Haram, who arrived in the capital, Abuja, earlier in the day. The girls were among hundreds abducted by the militant group from a school dormitory more than three years ago. A photograph of the event was posted on the president’s Twitter and Facebook accounts.

The president’s ill health has fuelled concern about his ability to rule the West African nation, which is experiencing its worst economic downturn in more than two decades. Buhari, president since 2015, returned to the country on March 10 after a seven-week medical leave to treat an undisclosed ailment in the UK, and has missed the past three weekly cabinet meetings.

The presidency released a 17-second video on May 5 showing Buhari making his first public appearance in three weeks, walking slowly after a prayer meeting at the presidential residence’s mosque. On May 2, Nigerian civil rights leaders urged the 74-year-old to take a second medical leave, saying his recent absences had “fuelled speculation and rumours”.