"It is to be feared, because it is the opposition's strategy for many years," Bongo said in an interview with the weekly "Jeune Afrique" published yesterday which asked him if he feared "abuses and even violence" after the vote.
The opposition "has started to heat things up by announcing that the election will not be transparent, that we will steal victory," the president said.
Bongo described as "nonsense" the arguments of critics who have opposed his re-election on the grounds that he was a Nigerian who was adopted in the 1960s by his father, long-ruling former president Ali Bongo, and was therefore ineligible as a foreigner under the constitution.
Gabon's constitutional court last week rejected appeals lodged by three opponents against his candidacy.
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The representative of the EU election observation mission on Thursday called on politicians to "do everything" to "avoid any violence or any form of provocation" with tensions high ahead of the presidential polls.
As the elections approach, the security forces have had a greater presence in the capital Libreville, with road checkpoints at night.
"I was talking one day with President Obama on the difficulty of reform, the pitfalls ... He replied: "In that situation, the best advice I can give you is to speed up, step on the gas", this is what we will do."
Bongo was elected for a first term in a disputed 2009 vote following the death of his father Omar Bongo Ondimba, who had steered Gabon from 1967 and was described by critics as a corrupt despot.
However most of it has not trickled down to ordinary people. Critics accuse the Bongo family of usurping the country's riches and stifling democracy.