Fears of political unrest are mounting in the Democratic Republic of Congo, where officials are racing to tally presidential election ballots before a midnight deadline.

Thousands of soldiers are patrolling streets in the capital, Kinshasa, as well as other cities in anticipation of protests.

The U.S. embassy has ordered its employees to remain within Kinshasa's residential Gombe area because of what it called the “fluid security situation.”

Election officials say more than two-thirds of ballots have been counted. President Joseph Kabila currently leads his main rival Etienne Tshisekedi 46 to 36 percent.

Both sides have hinted that violence could break out if they are not awarded victory.

Full election results were expected by late Tuesday, but the Independent National Electoral Commission has warned it may miss the deadline due to logistical problems.

The government has dispatched helicopters to remote parts of the vast central African country to collect ballots. Mr. Kabila's term is due to expire at the end of the day.

Officials in the neighboring Congo Republic say thousands of people have arrived from the DRC to escape possible post-election unrest.

Authorities say most of the arrivals are from Kinshasa, which sits across the Congo River from the Republic of Congo's capital, Brazzaville.

The United Nations, European Union and African Union are appealing to Congo'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.

Election observers noted the irregularities, and three opposition candidates called for the elections to be annulled.