Serious concerns are being raised about the counting of votes in the Democratic Republic of Congo's first multi-party elections in 40 years.
The final result may not be known for several weeks
International observers, who praised Sunday's relatively peaceful vote, say they have seen votes dumped and voting tallies that do not add up.
Human Rights Watch said foreign observers' work in the eastern region of Ituri was being severely restricted.
More than 25 million people were eligible to vote in the election.
Polling day saw a high-turnout of voters and very little violence.
Both the US-based Carter Center and the UN mission in the Congo (Monuc) hailed the process as generally peaceful and orderly.
But in recent days, concerns have grown over the counting of the ballots.
Anneke van Woudenberg, of Human Rights Watch (HRW), said she had seen for herself the dumping of large numbers of ballots outside counting offices.
There were also concerns over voting numbers that do not add up, a lack of verification of original ballot papers and an increasing number of null votes, she said.
She said international observers, including HRW, in Ituri "have been asked not to partake very much in the observation, not to ask questions, not to look at ballot papers... basically severely limiting the possibility of being able to observe the count."
Such concerns were echoed by observers in the capital, Kinshasa, where voting material has also been seen dumped and even burnt.
Colin Stewart of the Carter Centre - an independent body set up by former US President Jimmy Carter- said some officials had to wait three days for the ballots to be collected, and in the end had little option but to throw them into the back of trucks.
But he said that while things had fallen apart since polling day, there was nothing to suggest it was as a result of any widespread conspiracy.
"Certainly, the mess in the collection of data appears to be just a logistical mess," he told the BBC.
"The plan to collect materials appears not to have been thought through properly, and certainly wasn't implemented, and then attempts to rectify the situation actually made things worse."
Because of the large size of the country, a final tally is unlikely to be available for several weeks.
Thirty-two candidates, including incumbent Joseph Kabila, contested the presidency, while more than 9,000 candidates stood for parliament.
The voters were protected by 17,000 UN peacekeepers, most of them stationed in the east.