Ugandan opposition candidate Kizza Besigye has a lead of one percentage point over President Yoweri Museveni in the early counting process of Thursday's elections.
The count gave 48.5 percent to Besigye as against 47.5 percent for Museveni, based on 483,000 votes in the presidential election. This is Uganda's first multi-party vote for a quarter of a century.
There are 10.4 million registered voters in the country.
Although the figures came from 49 of Uganda's 69 districts, they were likely to be from urban areas where Besigye's support was strongest, analysts said.
The Electoral Commission has issued no official results.
Museveni, 62, in office since his rebels seized power in 1986, has been ahead in the opinion polls. However, he faces a strong challenge from Besigye, 49, whose Forum for Democratic Change has considerable backing from the young and in cities.
Western donors, who once hailed Museveni as one of a "new breed" of African leaders, were disappointed when the Parliament changed the constitution to allow him to stand for a third term.