WASHINGTON (AP) — President Barack Obama is urging both the winner and loser in Nigeria's presidential elections to work together to unify Nigeria.

Obama spoke separately on Wednesday with Muhammadu Buhari (moo-HAH'-mah-doo boo-HAH'-ree), who was declared the winner, and outgoing President Goodluck Jonathan.

The White House says Obama applauded Jonathan for putting the country and its people first by urging his supporters to accept the election outcome. In his call with Buhari, Obama thanked the president-elect for promoting calm and peaceful voting.

Obama is noting the challenges facing Nigeria, including the threat from the extremist group Boko Haram (BOH'-koh hah-RAHM'). He says the U.S. will keep supporting Nigeria as it confronts those challenges.

Buhari is the first opposition party candidate to win elections in Nigeria. His victory ended Jonathan's bid for another term.