Gabon's President Ali Bongo Ondimba is accusing his chief opponent of ballot fraud and a plot to seize power, after Bongo narrowly won re-election in a contested vote that sparked deadly clashes.

Election commission results showed Bongo beat challenger Jean Ping in the oil-rich central African country's Aug. 27 presidential vote by 1.57 percentage points. Opposition supporters have claimed fraud, and Ping declared himself the rightful winner.

Bongo lashed back on France's Europe-1 radio Wednesday, saying "Ping committed fraud" in his home constituency and others with the help of "cyber-criminals." Bongo did not elaborate on alleged ballot anomalies he said were found.

Ping, also speaking to Europe-1, dismissed the accusations and called for international help in determining "the truth."

International pressure is growing for transparency in the vote results.