A group of prominent Nigerians has called on President Muhammadu Buhari, 74, to take medical leave, amid growing concern about his health.
There was an “apparent deterioration” in his health following his failure to attend the last two cabinet meetings, the group said.
Mr Buhari took about seven weeks of medical leave in January, and flew to the UK for treatment.
When he returned home in March, he said he had never been so ill in his life.
Mr Buhari has not disclosed his illness, but hinted that he had had a blood transfusion.
Information Minister Lai Mohammed told the BBC that the president’s health was “a personal matter”.
Nigerians have been kept aware of his condition, he added.
The 13-member group included some of the Nigeria’s most influential civil society figures, including lawyer Femi Falana, political analyst Jibrin Ibrahim, and Transparency International Nigeria head Anwal Musa Rafsanjani.
In their statement, they said the president had not been seen in public for the last week, and his absence from the cabinet meetings, as well as the weekly Friday Muslim prayers, “has fuelled further speculation and rumours” about his medical condition.
The 13 said they felt “compelled” to ask Mr Buhari “to heed the advice of his personal physicians by taking a rest to attend to his health without any further delay”.
Mr Buhari’s personal assistant Bashir Ahmed said the president had met Justice Minister Abubakar Malami and other officials at the presidential villa on Tuesday as part of his official duties.
Last week, presidential spokesman Garba Shehu said Mr Buhari was “taking things slowly, as he fully recovers from the long period of treatment” in the UK.