The people of Gabon began casting their ballots Saturday in a vote to decide whether President Ali Bongo will remain in office or be unseated by a career diplomat and close associate of his late father, who ran the country for 41 years.

The election takes place in a climate of persistent social unrest driven in large part by the economic impact of the slump in the price of oil, which has long dominated Gabon's economy.

Bongo, 57, and ex-African Union Commission chief Jean Ping, 73, who both worked under Omar Bongo until he died in 2009, are seen as the only credible candidates among a field of 10.

In the working class district of Rio in the capital Libreville, a polling station set up at a school opened shortly before 8:00 am (0700 GMT) -- about an hour after the scheduled time, an AFP journalist said.

Elsewhere in the capital, voting had not yet started at several polling stations.

Until recently, Bongo was far and away the favourite, largely because several prominent politicians had declared themselves as candidates, thereby dividing the opposition.

But protracted negotiations led all the key challengers to pull out and put their weight behind Ping, with the last of them withdrawing only last week.

Some 628,000 of Gabon's 1.8 million inhabitants are eligible to take part in the election, whose winner will be decided by a simple majority after a single round of voting.

The campaign period has been acrimonious, marked by months of bitter exchanges between the two main camps, including accusations, and strenuous denials, that Bongo was born in Nigeria and therefore ineligible to run.

On Friday, each side accused the other of trying to gain an illicit advantage by buying up voter cards in various parts of the country for sums ranging from 10,000 to 50,000 CFA francs ($20 to $100).

Faced with repeated charges of nepotism, Bongo has long insisted he owes his presidency to merit and his years of government service.

His extravagant campaign was based around the slogan "Let's change together", playing up the roads and hospitals built during his first term.

In an overt jibe at Ping's long association with his father, Bongo has also stressed the need to break with the bad old days of disappearing public funds and dodgy management of oil revenues.

"There's a risk that certain people who did so much harm to our country will come back" to power, the president told a crowd of thousands during his last rally in the capital, Libreville.

- Former brother-in-law rival -

Ping has pledged to ensure, if elected, that Gabon would be "sheltered from need and fear," dismissing the president's much-touted moves to diversify the economy into rubber and palm oil as mere window dressing.

Despite boasting one of Africa's highest per capita incomes at $8,300, a third of Gabon's population live in poverty.

Unemployment among the young, according to the World Bank, runs at 35 percent.

Recent months have seen growing popular unrest and numerous public sector strikes as well as thousands of layoffs in the oil sector.

Fears that this discontent might degenerate into violence are fuelled by memories of what followed Bongo's contested victory in the 2009 presidential poll. Several people were killed, buildings looted, a ceasefire imposed and the French consulate in the economic capital Port-Gentil torched.

On Friday, UN Secretary-General Ban Ki-moon called on "all political stakeholders, in particular the candidates, to exercise restraint, abstain from any acts of incitement or the use of inflammatory statements, and maintain a peaceful atmosphere before, during and after the election."

He also urged the candidates to use "legal and constitutional channels" in the event of any dispute over the result.

Ping and Bongo go back a long way, having worked for years together under Bongo senior, who was responsible for getting Ping his job as chairman of the AU Commission.

Ping also has close family ties to the Bongo dynasty: he was formerly married to Omar Bongo's eldest daughter with whom he had two children.

Ping turned on Bongo in 2014, and in March he told French daily Le Monde that "Gabon is a pure and simple dictatorship in the hands of a family, a clan."

Source: AFP