Nigerian President Olusegun Obasanjo has defeated three challengers to become his party's nominee for the presidency in elections scheduled for April.

President Obasanjo scored a crushing victory in the ruling party primary election, winning more than 75 percent of the vote. His nearest rival, former Vice President Alex Ekwueme, took only 19 percent.

The other two candidates trailed even further behind, with less than five percent of the vote each.

Several of the challenges have complained that the voting system was unfair, and have threatened that unhappy party members might leave for other parties.

In a speech to delegates, Mr. Obasanjo called his nomination a victory for democracy and for the ruling party. But he cautioned that the real challenge will be uniting the party in order to win the general election, scheduled for April 19.

Mr. Obasanjo's nomination is a big step toward winning a second term in office. He is expected to face strong opposition in a country heavily divided along ethnic and religious lines.

Mr. Obasanjo said current Vice President Atiku Abubakar will again be his running mate. Analysts see the vice-president's support as key to winning over some of Mr. Obasanjo's critics within the party.

The president is a Christian from southwestern Nigeria, while Mr. Abubakar is a northern Muslim from the influential Hausa ethnic group.

Ethnic and religious violence has racked Nigeria over the last year, leaving hundreds dead. Mr. Obasanjo took office five years ago pledging to fight rampant corruption, but that battle has yielded few results and the economy has stagnated.

Nigeria has never had two successful, democratic elections in a row. The country has largely been ruled by military dictators since independence from Britain in 1960. Mr. Obasanjo's election in 1999 ended the most recent period of military rule.