(Adds details, background) LAGOS, Feb 21 (Reuters) - Nigerian President Muhammadu Buhari will fly to Saudi Arabia to discuss with king Salman ways to stabilise crude oil prices, the presidency said in a statement on Sunday. Buhari will also fly to Doha after his visit to the kingdom to discuss oil price stability with Qatar's ruler, the statement said. "Ongoing efforts by Nigeria and other members of the Organisation of Petroleum Exporting Countries to achieve greater stability in the price of crude oil exports are expected to be high on the agenda of discussions," the presidency said before the trip later this week.