Security forces have started to vote in the town of Dolisie, ahead of Wednesday s presidential election.
12 000 soldiers and police officers casted their vote.
According to the Congolese authorities, this would free up security forces, and allow them to focus on securing polling stations on Wednesday.
But most of the opposition candidates have pointed the move as an fraud attempt, that would give President Denis Sassou Nguesso a headstart in the election.
Bertrand Menier, of the Mouvement Ras-le-bol (Fed-up Movement), said the voters lists did not dissociate members of the military from civilians. We fear military personnel might vote twice, given that their names are on both civilian and military lists he said to Africanews.