Gabon's President Ali Bongo Ondimba, 64, took over from his father, Omar Bongo Ondimba, in 2009
Gabon's President Ali Bongo Ondimba, 64, took over from his father, Omar Bongo Ondimba, in 2009 AFP

Gabon's President Ali Bongo Ondimba said on Sunday that he would seek a third term as the oil-rich African nation's head of state.

The Bongo family has ruled the country for 55 years already and is branded a "dynastic power" by the opposition after Bongo, 64, took over from his father, Omar Bongo Ondimba in 2009.

"I officially announce today that I am a candidate," he told a crowd of supporters in a speech broadcast live on his Facebook page.

Presidential elections will be held on August 26.

His powerful Gabonese Democratic Party (PDG) holds strong majorities in both houses of parliament.

The president was narrowly re-elected in 2016, with just 5,500 more votes than rival Jean Ping who claimed the election had been fixed.

Announcement of the results sparked violence in the capital Libreville that killed four civilians and a policeman, according to the government, while the opposition says 30 people were shot dead by the security forces.

Bongo suffered a stroke in 2018 and spent months on the sidelines recovering, leaving the opposition to question his fitness to run the nation.

He still has a stiff arm and leg and has mobility difficulties, but in recent months has held "republican meetings" around the country and made official visits abroad, including for summits.

The failure of the opposition to agree on a single candidate for the presidential election left some 15 candidates to announce their intentions to stand.

Former minister Paulette Missambo, head of the National Union party, has said she will run, as has Alexandre Barro Chambrier, who served as a minister to the current president and his father.

The official closing date for candidates to announce their intention to run is Tuesday.

In April, the Gabonese parliament voted to amend the constitution and reduce the president's term from seven to five years.

Sections of the opposition criticised the changes, in particular the end of two rounds of voting, as a means of "facilitating the re-election" of Bongo.

The presidential ballot will coincide with elections for the National Assembly and regional and municipal councils, with July 11 set as the deadline for filing candidacies.

Gabon is one of the richest countries in Africa in terms of per capita GDP due largely to its oil revenue and relatively small population of 2.3 million.

Crude represents 38.5 percent of its GDP, and 70.5 percent of its export revenues.

Other areas of activity are manganese mining and forestry, but efforts to diversify the economy remain in low gear.

A third of the population live below the poverty threshold, according to the World Bank.