The Southern African Development Community (SADC) has called an emergency meeting on Thursday in Addis Ababa to discuss Democratic Republic of Congo's (DRC's) disputed presidential election, an adviser to President Joseph Kabila said.

Runner-up Martin Fayulu, who led pre-election polls, filed a fraud complaint on Saturday, asking for a recount after results gave victory to another opposition leader, Felix Tshisekedi.

Hearings into Fayulu's complaint opened on Tuesday at the Constitutional Court which has until Friday to render a judgment.

The December 30 election was meant to lead to Congo's first democratic transfer of power, but allegations of fraud cast doubt on the outcome and threatened to reawaken large-scale unrest in the vast Central African country.

Kabila's diplomatic adviser, Barnabe Kikaya Bin Karubi, told Reuters he would attend Thursday's SADC meeting. It was not immediately clear who else from Congo would be present or what action, if any, the bloc might decide to take.

SADC, which includes Congo allies such as South Africa and Angola, on Sunday called for a recount. South Africa and Zambia backtracked on Monday, although Zambia reiterated its call for a government of national unity.

Tshisekedi's Union for Democracy and Social Progress (UDPS) also plans to file a challenge on Tuesday to the results of the legislative election, which took place the same day as the presidential vote, UDPS spokesperson Vidiye Tshimanga said.

Although the presidential candidate of Kabila's ruling coalition, Emmanuel Ramazani Shadary, won only 24 percent of the vote, the coalition took more than 350 of 500 seats in the National Assembly, compared with about 30 for the UDPS.

That could undermine Tshisekedi's ability to live up to campaign promises to break with Kabila's long tenure, which began in 2001 when his father was assassinated.

"There are a certain number of inconsistencies between the numbers we have and those presented by the (electoral commission)," Tshimanga told reporters late on Monday. "A team of lawyers ... has prepared a case that will be filed to the competent authorities."

Fayulu alleges that Tshisekedi's win was the result of a backroom deal between Tshisekedi and Kabila that will let Kabila maintain control over important ministries and the security services.

Tshisekedi and Kabila deny there was any deal.

Congo's influential Catholic Church has also said the presidential results were inconsistent with those gathered by its 40 000 election observers.

It has not said who it believes won, but three diplomats briefed on its findings said they indicated it was Fayulu.