Observers at the Democratic Republic of Congo's landmark presidential run-off have generally praised its organisation, despite some disruptions.
A US spokesman said Sunday's poll was "light years ahead of anything" previously seen in DR Congo.
The vote is being rerun in the north-east town of Bumba, where polling stations were burnt, amid fraud claims.
The first unofficial results say President Joseph Kabila and ex-rebel Jean-Pierre Bemba are neck and neck.
The BBC's Arnaud Zajtman in the capital, Kinshasa, says the mood is tense, with European Union troops patrolling the streets and helicopters flying overhead.
The elections are supposed to draw a line under DR Congo's five-year war, which led to an estimated four million deaths and drew in the armies of at least six other African countries.
Former Mozambique President Joachim Chisano said the electoral "process had been well organised".
Former Canadian prime minister and head of the US-based Carter Center's observing team Joe Clark said: "There does not appear to be a trend of either intimidation or violence. One could almost say the opposite."
But at least one person was killed on polling day when police opened fire on Mr Bemba's supporters in Bumba, when they rioted after saying they had uncovered attempts to stuff the ballot boxes.
The AP news agency reports that voting began in Bumba around midday on Tuesday, after new voting materials were flown in.
The elections are to be held again on Wednesday in Fataki in Ituri district, where two election workers were shot dead on Monday by a drunken soldier, again sparking riots, in which 43 polling stations were destroyed.
The UN's Radio Okapi reports that the soldier responsible, Sergeant Mamale Innocent, has been sentenced to death for murder.
Results are being posted outside each of the vast country's 50,000 polling stations but the Independent Electoral Commission (CEI) has until 19 November to announce the winner of the poll.
Observers have compiled results from less than 5% of the polling stations and say there is little to choose between the two candidates.
These unofficial results show a similar trend to the first round, with Mr Kabila winning by a landslide in the Swahili-speaking east and Mr Bemba ahead in the Lingala-speaking west.
FIRST ROUND RESULTS
DR CONGO WAR
1998 - 2002
At least 8 armies, many rebel groups
2003: Rebels join unity government
East remains unstable
17,000 UN peacekeepers
These results imply that the support for Mr Kabila of the candidates who came third and fourth in the first round, both from the west, has done little to boost his support there.
Turn-out is reported to be lower across the country than in July's first round.
Mr Kabila won first round polls on 30 July, but fell just short of the 50% needed for outright victory.
Many Congolese fear that whoever loses the elections will resort to violence, as both men have considerable numbers of armed men and weapons at their disposal.
Both men have said they will accept the results, as long as they are free and fair.
DR Congo'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.
This country two-thirds the size of western Europe has just 300 miles of paved roads.
UN officials say the polls are the most important on the continent since the 1994 election that ended apartheid in South Africa.