Incumbent President Joseph Kabila, 40, in power since 2001, leads a divided opposition pack of 10 candidates going into the final stretch of the single-round vote.

The latest results, announced early Tuesday, give him 46.4% with just over two-thirds of polling centres counted. His top challenger, veteran opposition leader Etienne Tshisekedi, 78, has 36.2%.

Tshisekedi has made veiled threats of violence if Kabila wins.

"I call all our people to stay vigilant so that if needed they can execute the orders I will give them," he said Saturday.

The campaign saw deadly police crackdowns on Tshisekedi rallies and a series of clashes between the two rivals' supporters. Observers have warned the result announcement could plunge the country into chaos no matter who is declared the winner.

The International Crisis Group has put the country on its "conflict risk alert" list, citing clashes in Kinshasa on the eve of the polls, deadly rebel attacks in the south-eastern city of Lubumbashi on voting day, and a call from several opposition candidates for the vote to be annulled.

The result is expected late in the day, if at all.

The head of the Independent National Electoral Commission, Daniel Ngoy Mulunda, indicated early Tuesday that the commission, which has been plagued by delays and logistical chaos throughout the process, may not make its deadline.

"First of all we're going to make sure that all the results sheets have arrived and that we have all the information. If not, we won't be able to give you more than a partial report," he told journalists.

The supreme court has until December 17 to review the result and declare the official winner. Inauguration day is set for December 20.

Provisional parliamentary results are due in mid-January.

The elections are just the second since back-to-back wars from 1996 to 2003 in a country that remains one of the least developed in the world despite a wealth of cobalt, copper, diamonds and gold.

The central African giant has 32 million registered voters.