KAMPALA, Uganda — Ugandan voters lined up in parking lots, village squares and empty fields before dawn Thursday to choose between a leader who has ruled for 20 years and four challengers in the country's first multiparty elections in two decades.

Incumbent Yoweri Museveni and opposition leader Kizza Besigye were the top two candidates heading into Thursday's presidential election. Voters were also electing 284 members of parliament.

The balloting is the first multiparty elections in Uganda since 1980, a step forward after nearly 20 years of Museveni's "no party politics." But the same change to the constitution that allowed the participation of political parties also removed term limits on the president, allowing Museveni, 62, to run as many times as he wishes.

Some polling stations in the capital, Kampala, opened more than an hour late because of the delayed arrival of polling materials. But there were no reports of violence or other serious problems in the first hours of voting.

Final results were expected by Saturday afternoon, as required by Uganda law.

While few voters were willing to say whom they would choose, most said security and peace in the country were their highest priorities.

Mabel Kigozi, 38, said the tense campaign, which was marred by sporadic violence, made her nervous about the future of the country.

"The issue is to vote for a presidential candidate who can bring peace, unity and reconciliation, who can bring togetherness to Uganda," Kigozi said, declining to name her candidate. "I don't want war, violence, tribalism. I don't want that division."

Museveni appeared set to garner the most votes, according to opinion polls. The question was whether there he will take more than 50 percent, eliminating the need for a run-off election.

In recent years, Museveni has frustrated donors by intervening in neighboring Congo's civil war, increasing military spending and refusing to retire from politics as he had promised during the 2001 elections.

Last year, European nations suspended more than $32 million in budget support for the government. The partial cuts were accompanied by a warning that Uganda appeared be backsliding into authoritarian rule.

After Besigye returned from self-imposed exile last year to run against Museveni for a second time, prosecutors charged him with treason and rape and jailed him for three weeks. Museveni supporters also filed several civil court cases and appeals to have Besigye's candidacy nullified, efforts that were all eventually thrown out.

"This election right from the word go could never have been free or fair," Besigye told The Associated Press. "Our objective was to further expose this position both locally and internationally and to use whatever space would be available during the campaign to educate the population ... and to hopefully use the tremendous popular discontent to override all of these unfair situations."

Museveni's government has rejected all criticisms. He has advised Ugandans to ignore "foreign meddlers."

In an address to the nation on the eve of the vote, he told Ugandans that voting "is not a joke."

"It is a matter of life and death. If you decide wrongly, you will bear the consequences," Museveni said on state-run radio and television. "It has happened in the past. It can happen again."

Uganda's Electoral Commission has accredited 40,000 local and international observers to monitor the elections, which will take place at more than 16,000 polling stations for 10.4 million registered voters. The European Union, British Commonwealth and African Union all sent observers.