Ugandan President Yoweri Museveni held a comfortable lead in early poll results, with the veteran leader securing 71 percent of the 3.5 million ballots tallied so far.
According to the electoral commission, Museveni had garnered 2,432,864 votes while his main rival, Kizza Besigye, had only managed 781,353, giving him 22.9 percent of the vote.
The votes tallied so far represent a quarter of Uganda's 14-million electorate.
The electoral commission did not provide an accurate turnout figure, but said it would be higher than the 69 percent achieved for the 2006 presidential election.
Besigye, who accused the regime of planning to rig the election even before the polls kicked off, is conducting his own vote-counting in a secret tallying centre in Kampala.
The opposition leader's own partial returns suggest a much closer race. He has pledged to announce results later on Saturday.
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