Rivals to Central African Republic leader Francois Bozize pulled their representatives off the election body on Saturday, alleging fraud after early partial results from last weekend's poll put Bozize in the lead.
In the latest African election to run into dispute, candidates cited evidence of ballot-stuffing and irregularities during vote-counting in the former French colony, rich in diamonds, gold and uranium.
We have already launched legal measures for arbitration and we appeal to the international community to wake up to what is going on in Central African Republic, said ex-president Ange Felix Patasse, one of five candidates in last Sunday's vote.
National radio quoted Guy Samzung, head of the European Union delegation in the country, as saying he raised concerns with Bozize about imperfections and irregularities.
While no clear figures were available, returns from voting districts in and around the capital Bangui showed Bozize well ahead of Patasse, his nearest rival. Final results could come within days.
Bozize allies brushed off the wave of walk-outs from the cross-party election body, which now only consists of its president and spokesman.
They are resigning simply because, with partial results in, they have realised how unpopular they are, Bozize's campaign manager Sylvain Ndoutingai told reporters.
The dispute is the latest to highlight problems in Africa's efforts to stage elections.
Ivory Coast is in crisis with incumbent Laurent Gbagbo refusing to quit after UN-certified results showed him the loser of a November 28 poll. In Niger, there are concerns that its presidential poll on Monday has been inadequately prepared.
The Central African Republic poll was delayed three times due to lack of funds and trouble disarming rebels who have signed peace deals but still roam the northwest and the northeast.
The election was hoped to be a first step to addressing the instability that has prevented the former French colony from reaping the benefit of its resource riches.
Aside from home-grown insurgents, who often run rackets, extorting from traders and local populations, Lord's Resistance Army rebels who left Uganda years ago to roam across central Africa have moved into CAR's east, terrorising civilians.