Representatives of Congo's main opposition parties began talks this week in Pretoria on how to ensure the general election on December 20 will be fair and to decide on a potential joint candidate to challenge President Felix Tshisekedi.

A crowded opposition field of 25 candidates has been officially approved by the electoral commission in Democratic Republic of Congo to face Tshisekedi who is seeking a second term.

Campaigning for the election in Congo, the world's largest producer of battery material cobalt and a major copper producer, will start on November 20.

Opposition candidates include Tshisekedi's old rivals such as Martin Fayulu, a 66-year-old former Exxon Mobil executive who came second in the disputed 2018 presidential vote which he claimed to have won, and first-timers such as Congo's renowned Nobel Peace Prize-winning gynaecologist Denis Mukwege.

Fayulu told Reuters that discussions were to ensure that the elections were transparent.

"The question of a joint candidacy will certainly be discussed in due course," Fayulu said, adding that the main concern was to agree ground rules for holding peaceful elections.

A divided opposition field could be an advantage for Tshisekedi in a single round election that requires a simple majority of the vote to win.

Ahead of the 2018 presidential election, Fayulu was chosen as the joint opposition candidate in a deal that at the time included Tshisekedi, and the president's current Vice Prime Minister and Minister of the Economy Vital Kamerhe.

Both Tshisekedi and Kamerhe pulled out of the deal a day after it was agreed following what they said were protests from their supporters, and Tshisekedi went on to win the disputed vote.

MUKWEGE, KATUMBI AND FAYULU

Herve Diakese, a spokesperson for Moise Katumbi, a millionaire businessman and former governor of the copper-rich Katanga region said there was a need to bolster one opposition candidate.

"We're going to look for a leader, line up behind him and make him president," Diakese said. "Without discriminating against the others, the three names that stand out are Denis Mukwege, Moise Katumbi and Martin Fayulu," he added.

Albert Moleka, an advisor to Mukwege said that the joint candidacy must be based on programme, but the key to a fair election was for the opposition and civil society to be organised and monitor the vote.

"If we all go our own way, with fraud in the offing, can we win? How can we mobilise witnesses? How can we get around?," Moleka said.

Opposition parties have raised alarm and warned that the election could be flawed, alleging irregularities during the voter registration period orchestrated by the national election commission to favour Tshisekedi's ruling coalition. The commission has denied the accusation promising a fair election.