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.
01:03
Mozambique protests: Five dead, unrest disrupts key operations
01:01
Opposition parties in Namibia contest SWAPO's victory in the Presidential elections
01:04
Former ManCity striker nominated by Georgian Dream party for the presidential post
Go to video
Fugitive Zambian MP Emmanuel Jay Banda arrested in Zimbabwe after three-month Manhunt
00:58
Voting underway in Somalia's breakaway region of Somaliland
Go to video
US announces visa restrictions for Ghana