Gabonese Justice Minister Seraphim Moundounga has resigned in protest over the disputed presidential election.
He is reported to have warned the incumbent, Ali Bongo, that he could cancel the results of the election if they did not “tally with reality”.
Mr Bongo was declared the winner by a narrow margin last Wednesday, but the opposition say the poll was fraudulent.
His rival Jean Ping has called for a general strike and says dozens of his supporters have been killed.
Meanwhile, the European Union election observation mission to Gabon said there was a “clear anomaly” in results from President Bongo’s home province.
The African Union said on Tuesday it would send a delegation to Gabon to help resolve a post-election standoff.