Uganda's Electoral Commission chairman Badru Kiggundu has extended voting hours from 4pm (1300 GMT) to 7pm (1600 GMT) in areas in which voters were unable to cast their votes earlier.
He says the extension has been prompted by the electoral body's delay on Thursday morning to deliver voting materials at various polling stations across the country.
Section 50 of the Electoral Commission Act grants the electoral body to extend voting time.
Voters in Kampala and Wakiso districts, according to EC should proceed to vote.
Earlier, Ugandan police fired tear gas to disperse furious voters Thursday in the capital Kampala as the election commission apologised for hours-long delays in delivering ballot papers, AFP reporters said.
Voting was due to begin at 7am (0400 GMT) but was stalled for several hours in some polling stations in the city and surrounding Wakiso district when ballot boxes and papers did not arrive on time.
The capital traditionally shows strong support for the opposition.
"There has been a delay in delivery of polling materials in some parts of Wakiso district and Kampala capital city. The Electoral Commission regrets the delay," the commission said in a statement.
"The polling materials have now been delivered to all these places and polling has commenced in most of the places," the statement added.
Ugandan authorities also blocked social media platforms and mobile money networks as voting in the General Election got under way citing concerns over "national security".