38-year-old pop star Bobi Wine is challenging one of Africa’s longest serving leaders in Uganda’s hotly contested election.
Robert Kyagulanyi, known by his stage name Bobi Wine, says he represents the country’s younger generation, while Yoweri Museveni, 76, says he is standing for stability.
Earlier in the week, access to all social media was blocked after Facebook banned several accounts which backed the ruling party.
Ugandan police say they will deploy officers on rooftops of the capital Kampala on election day, while armoured vehicles have started patrolling the streets.
Polls were due to open at 07:00 local time (04:00 GMT) but voting was delayed in several areas.
Results are not expected before Saturday.
President Museveni is seeking his sixth elected term in office after 35 years in power.
Campaigning had been banned in the capital Kampala, and several other districts. The opposition says this is because it is popular in those areas, but the government says it was to prevent the spread of Covid-19.