Nigeria's Independent National Electoral Commission (INEC) chairman Mahmood Yakubu (L) presents to Nigerian President Muhammadu Buhari his certificate of election after he was re-elected on February 27, 2019, in Abuja. - Muhammadu Buhari was on February 27 re-elected Nigeria's president after a delayed poll that angered voters and raised political temperatures, but the opposition immediately vowed to challenge the "sham" result in court. (Photo by Kola SULAIMON / AFP)