Nigerian President Muhammadu Buhari returned from more than three months of sick leave in London to a nation agitated by a sluggish economy, re-emerging ethnic tensions and resurgent attacks by Islamist militants in the northeast.

Buhari, who left Nigeria on May 7 for medical tests, arrived in the West African nation’s capital, Abuja, on Saturday, and walked briskly to the airport building.

Mr. President is scheduled to address the nation in a broadcast at 7 a.m. local time on Monday, the State House said in an emailed statement, according to Bloomberg.

Buhari’s return marked the end of the second prolonged visit this year by the 74-year-old head of Africa’s biggest oil producer to the U.K. for treatment, after a seven-week stay between January and March.

On both occasions, he handed over power to Vice President Yemi Osinbajo.

The nature of the illness hasn’t been disclosed.

While Nigerian officials have said there was no cause for alarm, Buhari’s absence fueled concern about his ability to rule the nation, whose economy contracted in 2016 for the first time since 1991 amid low revenue from crude exports.

Coup rumors surfaced in May when Army Chief of Staff Tukur Buratai said he’d received information about individuals approaching soldiers and officers to discuss a plot.

The armed forces dismissed new speculation last month that there was a conspiracy to topple the government.