The joint call by 17 candidates at a news conference in Libreville was their first public statement since Thursday's announcement of Ali Ben Bongo's victory triggered violent street clashes and looting in the central African oil producer.
"We demand a recount of the vote that was interrupted by the president of the electoral commission, on the basis of returns from all polling stations," the candidates, including runner-up ex-interior minister Andre Mba Obame, said in a statement.
"We call on the Gabonese people to remain mobilized and vigilant for progressive action," they said, without elaborating further on what form that action would take.
They called for an international inquiry to "determine the seriousness of events, the violations of human rights and the responsibilities for this veritable blood bath".
At least two were reported killed in rioting and looting in the oil hub Port Gentil last week before authorities imposed a curfew and reinforced troop and police numbers. The capital Libreville also saw brief street protests.
