FILE PHOTO - Nigerian President Muhammadu Buhari in Abuja, Nigeria February 11, 2016. REUTERS/Afolabi Sotunde/File Photo

ABUJA (Reuters) - Nigeria’s ailing President Muhammadu Buhari, who had nearly two month’s medical treatment in Britain earlier this year, should take medical leave immediately, civil society leaders have said in an open letter.

The 74-year-old president returned home in March and said he would need more rest and health tests. Details of his medical condition were not disclosed.

In a letter titled “President Buhari should take medical leave immediately”, a group of political activists noted his absence from the last two weekly cabinet meetings and speculation about his ability to run Africa’s most populous nation and biggest economy.

“We are compelled to advise him to heed the advice of his personal physicians by taking a rest to attend to his health without any further delay,” they said in the letter dated May 1.

The letter was signed by 13 civil society leaders including human rights lawyer Femi Falana and Jibrin Ibrahim, an academic at a think-tank based in the capital Abuja.

Femi Adesina, one of Buhari’s spokesmen, declined to comment on the letter. Garba Shehu, another presidency spokesman, last week said Buhari received daily briefings on activities of government and met his vice president regularly.

He also said Buhari was spending most of his time in his private residence, which is equipped as an office, adding that he had gone through the worst period of his recovery in London.