President John Mahama, in his capacity as Chairman of the Economic Community of West African State (ECOWAS), has congratulated Nigeria's President-elect, Muhammadu Buhari, after a historic election victory.

The statement released Wednesday also commended incumbent President, Goodluck Jonathan, for his "leadership and statesmanship" by accepting the results declared on Tuesday March 31, 2015.

"ECOWAS also notes the high sense of duty and professionalism exhibited by the Independent National Electoral Commission led by Professor Attahiru Jega, which was a significant factor in the success of the elections", the release said.

Mr Buhari's All Progressive Congress won by an excess of two million votes after polling 14,954,400 to beat Jonathan's People's Democratic Party which polled 12,827,522.

The former military leader's victory at the polls held on March 28 is the first of such triumphs by an opposition candidate in Nigeria's democratic history.

ECOWAS Chair, John Mahama, also commended the people of Nigeria for their determination and courage throughout the election period.

"This is a clear indication of the collective commitment of the Nigerian stakeholders towards strengthening democracy and good governance in line with our Community Protocols.

"ECOWAS urges all political parties, candidates, their supporters and the general public to accept the verdict of the Electoral Commission, continue to observe the atmosphere of peace and employ exclusively legal and constitutional means to seek redress for any grievances", the statement admonished.