A second African regional body has called for a recount in Democratic Republic of the Congo's (DRC) contested presidential election, raising pressure on Kinshasa to fix a dispute that could fan unrest.

The International Conference of the Great Lakes Region (CIRGL), a 12-member body including DRC allies Angola and the Republic of the Congo, expressed "great concern" at the controversy surrounding the poll results.

"We suggest that the competent structures consider counting the votes in order to guarantee the transparency of the results," it added in a statement.

The December 30 vote was supposed to herald Congo's first democratic transfer of power in six decades of independence and a new era after President Joseph Kabila's chaotic 18-year rule.

But monitoring groups noted widespread irregularities, including faulty voting machines and poorly run polling stations, overshadowing talk of democratic progress in the vast country of 80 million people.

Second-place finisher, former Exxon Mobil executive Martin Fayulu, says he in fact won by a landslide with over 60 percent of votes and that the official winner, opposition leader Felix Tshisekedi, struck a deal with Kabila to be declared the victor.

Tshisekedi and Kabila deny this.

International pressure on Kabila has built since the vote, in part because Congo's influential Catholic Church said tallies by its 40,000-strong monitoring team show a different winner to that announced by the electoral commission.

France, Belgium, the United States and the United Kingdom have all expressed concern about the vote. But perceived criticism from inside Africa could hold greater sway in Congo.

The CIRGL statement late on Sunday echoed a statement from the Southern African Development Community (SADC), which contains allies of Kinshasa like South Africa and Angola.

Approval of the election results from regional partners is critical for the legitimacy of president-elect Tshisekedi.

Spokespeople for Kabila and Tshisekedi were not reachable for comment on the statements from African bodies.

Fayulu has welcomed calls for a recount.

Isolated post-election violence in the country has many fearing a return to the kind of conflict and upheaval that killed millions since the 1990s and destabilised the region.

The DRC is the world's leading miner of cobalt, a mineral used in electric car batteries and mobile phones, and Africa's biggest copper producer. It also mines gold and diamonds.