ABUJA, Nigeria (AP) — Nigeria’s president was departing Sunday night for further medical checkups in London, renewing fears over his health after he spent weeks overseas on medical leave earlier this year and said he’d never been so sick in his life.

The announcement came shortly after 74-year-old President Muhammadu Buhari met at his official residence with the 82 Chibok schoolgirls freed this weekend from three years of captivity by Boko Haram extremists.

The latest medical leave startled Africa’s most populous nation even as it rejoiced in the schoolgirls’ return.

Buhari has missed three straight Cabinet meetings and is said to spend most of his time working from home. On Friday, the government released images of his first public appearance in a week as he attended Friday prayers.

The nature of the president’s illness remains unclear. On his return from his earlier medical leave in London in March, Buhari made reference to blood transfusions.

That earlier absence led some to call for Buhari’s replacement.

Photos from his meeting with the freed schoolgirls Sunday night showed the rail-thin leader standing and addressing his audience.

A statement from the president’s office said Buhari had delayed leaving for London earlier Sunday so he could meet with the schoolgirls.

“There is no cause for worry” about this latest medical leave, the statement said, adding that the length of Buhari’s stay in London will be determined by his doctors.

After his return from London earlier this year, Buhari had indicated that further checkups might be needed.

The president’s office said Vice President Yemi Osinbajo again will be in charge while the president is out of the country.