Zambians formed long lines at polling stations on Thursday in a tight election race for president and parliament that has been marred by violence between rival factions.
There were no early reports of unrest during voting in a country whose peaceful transitions of power in the past have been held up as a democratic model in Africa. However, officials were anticipating tension after the close of voting and the final announcement of results. A winner must get more than 50 percent of the vote to avoid a runoff election.
"I came early here so that I can vote, then go and rest since it's a holiday today," said Chanda Chileshe, a voter at a polling station.
Early results are expected late Thursday, and officials plan to announce the final tally within 48 hours.
President Edgar Lungu of the ruling Patriotic Front party faces businessman Hakainde Hichilema of the opposition United Party for National Development. Mr. Lungu won the last election with 48 percent of votes, taking office in early 2015 after the death of President Michael Sata. Mr. Hichilema, a close second in that election, called the vote a sham.
Allegations of election irregularities have also dogged the current campaign, which was suspended for 10 days last month in the capital, Lusaka, after a supporter of Hichilema's party was shot dead amid a protest over police canceling a political rally.
In addition, international rights groups have expressed concern over the alleged stifling of some local media. The government closed the country's largest privately owned newspaper, The Post, in June over unpaid taxes of about $6 million, but the paper's owner said it was meant to silence him before the vote. The paper has been a vocal government critic.
Zambia's economic woes have contributed to the unease. Plunging prices for Zambia's main export, copper, have closed mines, leaving thousands unemployed. Economic growth has been roughly cut in half, and the country this year asked the International Monetary Fund for help.