Ping lodged a complaint Thursday with the Constitutional Court, his campaign team told CNN, demanding a vote recount.
"I am committed to defend the vote of Gabon," Ping said in a statement after meeting Friday with supporters in Libreville, the capital.
"If the Gabonese people do not recognize themselves in the decision handed down by the Constitutional Court, I will stand by their side, by the side of the people to demand they respect Article 9 of the constitution that states unambiguously that the election of the president of the republic is gained by the candidate who obtains the most votes," he said.
Ping, a diplomat and former African Union official, lost the presidential bid to incumbent Ali Bongo by less than 6,000 votes, according to figures from the country's electoral commission.
The results, released August 31, show that Bongo won 49.8% of the vote, while Ping had 48.23%. Ping and his supporters say the numbers are fraudulent and demand a recount.
EU mission notes voting 'abnormalities'
International observers reported some irregularities with the count and asked the electoral commission to publish the results for each individual polling station.
The European Union's election monitoring mission in Gabon said Tuesday
that the 99.03% turnout in the province of Haut-Ogooué, Bongo's stronghold, was nearly double the national average. It said analysis of the votes in the province revealed "obvious abnormalities."
Bongo has refuted those assertions and contested some of the figures in areas that favored his opponent.
Following days of political impasse and back-and-forth between the campaigns, both candidates now claim to be the president.
The United States, France and the United Nations expressed concern over the crisis and joined the call for the government to release the results of each polling station.
"Elections must credibly reflect the will of the people," US State Department spokesman John Kirby said. "We call on the Gabonese government to release results for each individual polling station. This will help give the people of Gabon, as well as the international community, confidence the announced vote tallies are accurate. "
Deadly violence, arrests, media blackouts
People took to the streets after the results of the presidential election were announced. Violence erupted in the Gabonese capital as opposition supporters clashed with police.
The Parliament building was set on fire, and shops and businesses were looted. At least three people died in the clashes, according to Gabon's Interior Ministry. Hundreds were wounded.
As many as 800 people were arrested in Libreville on suspicion of looting and disturbing the order, according to the ministry. Up to 300 more were arrested elsewhere in the country.
Some residents said they haven't been able to get in touch with loved ones, fearing they may have been detained in the protests. Communications blackouts were reported, including temporary suspension of the Internet.
Several French nationals were unaccounted for after the post-election violence, French Foreign Minister Jean-Marc Ayrault said in a statement Monday.
"Arrests have been made in the past few days. France has had no news from several of its compatriots," he said.
A high-level international mission of African Union and UN senior officials was set arrive Friday in Libreville to help ease tensions, but the Gabonese government announced the indefinite postponement of the mission, the United Nations said.
Bongo succeeded his father, Omar Bongo, in 2009, when similar clashes erupted. The elder Bongo took power in 1967, seven years after the country's independence from France.
Ali Bongo's re-election would extend his family's half-century rule over the oil-rich nation of nearly 1.8 million by another seven years.
Despite Gabon's oil wealth, a large percentage of the population lives in poverty.
Ping, a long-serving politician in Gabon's government and former AU Commission chair, is promising change. The son of a Chinese father and Gabonese mother, Ping is married to the daughter of Omar Bongo.