Buhari spent over three months in London for treatment.
Nigerian president Muhammadu Buhari addressed the nation in a televised speech on 21 August following his return to the captital Abuja after more than three months of sick leave at a London hospital.
Buhari, who has defied repeated calls to stand down, used his televised speech to condemn demands by separatists for the independence of southeastern Nigerian state of Biafra. He said Nigeria's "unity is settled and not negotiable", condemning the actions of "irresponsible elements" and "political mischief makers."
The 74-year-old had been receiving treatment for an unspecified illness in London since 7 May, returning to Nigeria on 19 August. He had also been on prolonged sick leave in London earlier this year.
Buhari returns to a country threatened by re-emerging ethnic tensions, a weak economy, and resurgent attacks by Islamist militant Boko Haram in the north east.
Buhari was elected in March 2015 and is half-way through his four-year term of office which ends in 2019.