Democratic Republic of Congo's (DRC's) electoral commission met all night and into Wednesday morning ahead of an announcement of results from the presidential election that could come later in the day.

Riot police were deployed in front of the commission headquarters in the capital Kinshasa and along the city's main boulevard, as Congo braced for possible violence amid accusations of vote fraud and suspicions that the government was negotiating a power-sharing deal with one opposition candidate.

The December 30 poll was meant to lead to the vast Central African country's first democratic transfer of power in its 59 years of independence, but a disputed result could trigger the kind of violence that erupted after the 2006 and 2011 elections and destabilise Congo's volatile eastern borderlands.

The electoral commission (CENI) announced on Tuesday evening that it had initiated "a series of evaluation meetings and deliberations, at the end of which it will proceed to the publication of provisional results from the presidential election".

A CENI source and a diplomat said they expected results to be announced later on Wednesday. Another diplomat, however, said that not all the vote tallying had been completed and that the announcement might have to wait until Thursday.

People deserted the streets of the eastern city of Goma on Tuesday evening after a rumour spread that the announcement was imminent. The results were originally due last Sunday but were postponed due to delays tallying the vote.

President Joseph Kabila is due to leave office this month after 18 years in power and backed his former interior minister, Emmanuel Ramazani Shadary, in the election.

Shadary was competing against two main opposition candidates, businessperson Martin Fayulu and Felix Tshisekedi, the president of Congo's largest opposition party.

Tshisekedi's camp, which says it expects to win, said on Tuesday that it had met with Kabila's representatives to ensure a peaceful transfer of power, although Kabila's camp denied any such meetings had occurred.

Supporters of Fayulu, who had a healthy pre-election poll lead, have voiced suspicions that Kabila may be looking to negotiate a power-sharing agreement with Tshisekedi if Shadary loses.

On Tuesday, Fayulu and six other presidential candidates issued a statement saying that "the electoral results cannot be negotiated and under no circumstances will we or the Congolese people accept such results".

Tshisekedi's spokesperson, Vidiye Tshimanga, on Wednesday sought to play down the contacts with Kabila's representatives, saying they had occurred only on the sidelines of meetings with the CENI and regional observers about the electoral process.