Gabon's opposition candidate Jean Ping is decrying a constitutional court ruling that rejected his appeal of the disputed election.

The court announced early Saturday that incumbent President Ali Bongo Ondimba won the Aug. 27 vote despite concerns raised by the opposition and international observers.

Ping vowed Saturday that he would not back down, and he called on his supporters to mobilize.

There was a heavy security presence around Libreville, the West African nation's capital, on Saturday, with troops keeping a watchful eye on residents.

The opposition says as many as 100 people have been killed while 1,200 others have been detained by authorities as part of a government crackdown.

Bongo came to power in 2009 after his father, Omar Bongo, died after 42 years as president.