Ugandans started casting their votes in the presidential and parliamentary elections on Thursday, but several stations in the capital Kampala were facing delays and awaiting ballot papers, an AFP reporter said.
Voting was due to begin at 07:00 am (0400 GMT) but, despite queues forming outside polling booths, many had still not opened over an hour later.
Ugandans are to decide whether to give Yoweri Museveni, a 71-year-old former rebel fighter who seized power in 1986, a fifth term in office.
The polls opened amid tensions, as an opposition supporter was shot on Monday during clashes with police at a campaign event in Kampala.
All sides contesting in the elections accuse each other of provoking tensions and assembling vigilante groups as the leading opposition candidates talk of possible vote rigging.
President Museveni faces a challenge from seven candidates, but his two main challengers are longtime opposition leader Kizza Besigye, who has run unsuccessfully in three previous elections, and former Prime Minister Amama Mbabazi, who until recently was a close ally.
On the streets of Kampala, most young voters - who reflect a large majority of the country- identify themselves as Besigye supporters.
Joel Nyonyintono, a 26-year-old entrepreneur, said he was ashamed of the condition of Uganda's roads and hospitals, adding that the country needed an innovative leader.
"We are so far behind. We need to open our eyes and move into the 'now' tense," he said.
Other voters believe Uganda is not ready for a post-Museveni era.
"We have had peace for a long time and these young people are taking it for granted because they don't know how it was before him," said Nanteza Beatrice, 56, a fruit vendor in a Kampala market.
Museveni who is widely predicted to win another term, is hailed by many Ugandans for providing decades of relative peace and economic stability, after waging a five-year guerrilla war before coming to power.
Over 15 million Ugandans are registered to vote in polls which are due to close at 04:00 pm (1300 GMT).
Initial results are expected as early as Saturday afternoon with the leading candidate requiring more than 50 percent of votes cast to avoid a second round run-off.