With most of the votes counted, Democratic Republic of Congo President Joseph Kabila appears headed for re-election, though full results have been delayed until Thursday.
Results from nearly 90 percent of the country's polling places show Kabila in the lead with almost 50 percent of the total vote. His closest challenger, Etienne Tshisekedi, has 33 percent.
Supporters of both men have hinted that violence could break out if their candidate is not awarded victory.
Troops in the capital of Kinshasa and other major cities are on standby, in case of unrest.
The electoral commission was scheduled to reveal the final outcome Tuesday but delayed, saying it would not have a full count until Thursday.
The delay means President Kabila has remained office past the end of his term, which expired at midnight Tuesday (UTC 22:00).
Kinshasa has been largely quiet so far, except for an incident Tuesday when police used tear gas to disperse supporters of Tshisekedi, near the headquarters of his party.
On Tuesday, the U.S. embassy ordered its employees to remain within Kinshasa's residential Gombe area because of what it called the "fluid security situation."
Officials in the neighboring Congo Republic say thousands of people have arrived from the DRC to escape possible post-election unrest.
The United Nations, European Union and African Union are appealing to the DRC's people and political figures to remain calm and avoid bloodshed.
Last week's balloting was only the second free election since the African nation was torn apart by several years of warfare that ended in 2003.
Voting was supposed to last for one day but stretched into three because of ballot shortages and scattered incidents of violence.
Human Rights Watch says at least 18 people were killed in violence leading up to last week's vote.