Presidential elections
Zambian opposition leader Hakainde Hichilema cast his vote at a polling station in Lusaka on Thursday.
Hichilema of the United Party for National Development (UPND) is incumbent President Edgar Lungu's main challenger.
His campaign has ridden on public frustration over Lungu's economic policies which have been criticized for exposing the copper producer to high debt and soaring food prices.
After casting the vote, Hichilema told reporters that polling workers were being slow with people stranded in long queues.
"I'm just concerned about the slowness of the process. There are thousands of people, they need to vote," he said.
Hichilema is seeking the presidency for the sixth time.
Lungu voted shortly after polls opened at 6am (0400 GMT).
"We are winning, otherwise I wouldn't have been in the race if we were not winning, we are a winning team," the upbeat Lungu told reporters outside a nursery school in Chawama, a poor neighbourhood of Lusaka.
11:17
African central bank governors revive vision for continental monetary integration {Business Africa}
01:09
Guinea Bissau goes to polls with president seeking a second term in office
00:54
Ugandan Police block NUP in Arua ahead of elections
00:56
Madagascar’s New Leader Randrianirina outlines bold Roadmap in first national address
Go to video
Court weighs bid to disqualify CAR president Touadéra from election
02:28
Zambia's eco-friendly beekeeping helps combat deforestation