Democratic Republic of Congo President Joseph Kabila has a strong lead over his rival, with most votes counted from the presidential run-off, results show.
Joseph Kabila (l) is leading Jean-Pierre Bemba (r)
Mr Kabila has 61%, while former rebel leader Jean-Pierre Bemba has 39%, according to results on the Independent Electoral Commission (CEI) website.
Peacekeepers have increased their patrols in the capital fearing violence when final results are announced.
Mr Bemba's supporters have claimed they have evidence of rigging.
Votes counted: 65%
United Nations observers say the election is the most significant in Africa since Nelson Mandela was elected as South Africa's president in 1994.
The elections are the first since the end of DR Congo's five-year civil war, in which up to four million people died.
They are seen as the country's first free elections since independence in 1960.
Turnout was 67%, with 65% of the votes counted, according to the CEI.
The commission has until 19 November to announce the results and stresses that no "trend projection" can be made on the basis of the provisional results.
UN peacekeepers provided logistical support for the vote
Both men have pledged to respect the outcome of the election.
The first round of elections showed a regional divide, with Mr Kabila gaining a landslide in the Swahili-speaking east, while Mr Bemba got most support in the west, where Lingala is the common language.
The world's largest peacekeeping force - 17,000-strong - is in DR Congo, tasked with ensuring security.
At least 23 people were killed in gun battles between security forces loyal to the two men in the capital, Kinshasa, after the announcement of first round results.
Mr Kabila won 45% of the vote, while Mr Bemba got 20%.
International observers generally praised the vote as being well-run, despite some disruptions in the north-east of the country.
The election was intended to close the door on decades of dictatorship and conflict.
Counting the votes is a time-consuming process as all the ballot papers had to be transported from sometimes remote locations to compilation centres.
DR Congo is two-thirds the size of western Europe and has just 300 miles of paved roads.
The country's rich reserves of minerals such as gold, diamonds and coltan - used in mobile phones - have attracted a series of armed groups, both Congolese and foreign, intent on looting.