LIBREVILLE, Gabon — Opposition candidate Jean Ping vowed to not back down from his pursuit of the presidency hours after the constitutional court upheld the victory of incumbent President Ali Bongo Ondimba, whose family has been in power for nearly half a century.

It was not immediately clear what additional recourse Ping might pursue in the aftermath of the announcement Bongo had won by 50.66 percent of the vote. Ping and his supporters have accused the ruling party of vote-rigging, and the opposition leader reiterated his call Saturday for people to object.

“This decision does not bring the Gabonese people together and it does not appease them because they don’t recognize it, nor does the international community, which gives it no value,” Ping said.

“I will not back down,” he said. “As I promised you as the president clearly elected by the Gabonese, I will remain by your side to defend your vote and your sovereignty.”

Ping’s refusal to concede raises the specter of prolonged unrest in Gabon, the oil-rich nation where Bongo became president in 2009 after the death of his father. The late Omar Bongo ruled the country for more than four decades, and was accused of siphoning off oil profits to enrich his family and associates.

Already the opposition has said that as many as 100 people have been killed while some 1,200 have been detained by authorities as part of a government crackdown on dissent.

On Saturday, there was a heavy security presence around the capital of Libreville, with troops keeping a watchful eye on residents.

Bongo thanked his supporters In a victory speech and underscored the challenges ahead following such a close election.

“The tight margin of this victory means there are many voters who, for one reason or another, did not choose us,” he said. “We must decipher their message, hear and understand it.”

International observers had raised doubts about results in one Bongo stronghold where he won 95 percent of the vote and turnout was reported to be 99.9 percent. However, the constitutional court said that the results still showed that Bongo had won the national election regardless.

Larson reported from Dakar, Senegal.