Nigeria’s electoral commission delayed the presidential election until Feb. 23, making the announcement a mere five hours before polls were set to open Saturday. It cited unspecified “challenges” amid reports that voting materials had not been delivered to all parts of the country.

“This was a difficult decision to take but necessary for successful delivery of the elections and the consolidation of our democracy,” commission chairman Mahmood Yakubu told reporters in the capital, Abuja. He said more details would be released during an afternoon briefing.

Nigeria also postponed the previous presidential election in 2015 because of deadly insecurity in the northeast, which remains under threat from Islamic extremists.

More than 84 million voters in this country of some 190 million had been expected to head to the polls in what is seen as a close and heated race between 76-year-old President Muhammadu Buhari and top challenger Atiku Abubakar, a billionaire former vice president.