Libreville, Gabon - Gabon's opposition leader has warned of further instability if judges do not heed his call to recount votes after a closely fought presidential election.

Jean Ping's warning came after he filed a petition challenging the election results, and after two weeks of sporadic violence.

"I fear that if they [judges] make a wrong judgment, Gabon will be unstable," he said at opposition headquarters in the capital Libreville. "They have to choose between stability and instability. It's a heavy responsibility but I hope they make judgment that is beyond passion."

Ping lost the August 27 presidential election to incumbent Ali Bongo by only 6,000 votes.

In his court petition, Ping requested a recount of votes from President Bongo's home province of Haut-Ogooue, and for the election result to be nullified.

READ MORE: Gabon's Jean Ping challenges result in court

His supporters celebrated his decision to file a petition. Gathering in Libreville as they awaited his arrival at the headquarters, dozens cheered and chanted pro-opposition slogans.

The atmosphere, though, turned hostile when a journalist who works for the national broadcaster turned up,. underlining the tension that still exists.

The opposition and some rights groups have said dozens were killed in violence between protesters and police after the vote. Hundreds went missing in a crackdown on dissent, they have said.

Government leaders contest those figures, saying that at least four people were killed and more than 1,000 people were arrested.

"There's a lot of news from politicians that say 50 people have been killed, but you need to verify this information by going to hospitals and mortuaries," said Interior Minister Pacome Moubelet Boubeya, as he addressed journalists. "I'm surprised to hear this figure. Give me a list of names and I'll look into it."

President Bongo and his ministers have said that there were election irregularities in opposition strongholds that must be investigated.

Judges at the constitutional court have two weeks to either throw out the opposition's complaint or invalidate the election results.

Follow Catherine Soi on Twitter: @c_soi