LIBREVILLE, Gabon — Gabon’s top opposition candidate Jean Ping declared Friday that he was the rightful winner of the presidential election, accusing the country’s incumbent leader of using fraud to cling to power.

The move sets the stage for a protracted dispute over the election, as President Ali Bongo Ondimba also has declared victory.

On Friday, Ping called for the release of results from individual polling stations. Results released by election officials showed Bongo won by a mere 1.57 percentage points.

“The whole world knows today who is the president of the Republic of Gabon. It’s me, Jean Ping,” he told reporters.

“Each time the Gabonese people have chosen their president, the dark forces are always gathered to place he who was not chosen as head of state. Together we have decided that this time things however will be different.”

Bongo’s father had ruled the oil-rich country since the 1960s until his death in 2009 when his son then came to power.

Ping’s supporters already have taken to the streets in protest, and at least three people have been killed in the unrest. On Friday, Ping said citizens had “strongly demonstrated their legitimate anger.”

The U.S. Embassy in Libreville said in a statement on its website Tuesday that Gabon’s voters were not “well served by the many systemic flaws and irregularities that we witnessed,” including the late opening of polling stations and “last minute changes to voting procedures.” The embassy said the government should publish results by polling station.

European Union observers have criticized a “lack of transparency” on the part of institutions organizing the vote.