Gabon's main opposition parties, who have lined up behind a single candidate to challenge Ali Bongo Ondimba in next week's presidential vote, on Sunday urged a boycott of legislative contests the same day, after a last-minute change to voting rules.
Former education minister Albert Ondo Ossa secured the backing of the Alternance 2023 opposition grouping on Friday, hoping to unseat Bongo, whose family has ruled the oil-rich West African state for 55 years.
Last month, however, Gabon's electoral commission announced that any vote for a local deputy would automatically be a vote for that deputy's presidential candidate.
The move was denounced by critics as favouring the ruling Gabonese Democratic Party (PDG), since Ondo Ossa is not backed by any single party, and therefore will not have corresponding candidates for the parliamentary vote.
During a rally in Libreville broadcast on social media, Ondo Ossa and Alternance 2023 officials warned of an "unfair vote" that violated the separation of executive and legislative powers.
They urged a boycott of the parliamentary elections, calling instead "to vote only for the president" and to "throw the legislative ballot sheets in the trash".
Ondo Ossa had already told AFP on Friday that if elected, "I will dissolve parliament and convene new elections" for the body.
Launched in January, Alternance 2023 brings together six opposition groupings in a bid to defeat Bongo, who took over from his father Omar Bongo Ondimba in 2009 and announced his re-election bid in July.
The president was narrowly re-elected in 2016, with just 5,500 more votes than rival Jean Ping, who claimed the election had been fixed.
Bongo suffered a stroke in 2018 and spent months on the sidelines recovering, leaving the opposition to question his fitness to run the nation.