Army officers have appeared on national television in Gabon to say they have taken power. They said they were annulling the results of Saturday’s election, in which President Ali Bongo was declared the winner. Military officials later said that Mr Bongo had been placed under house arrest and one of his sons arrested for treason.

His overthrow would end his family’s 53-year hold on power in Gabon.

Gabon is one of Africa’s major oil producers, while nearly 90% of the country is covered by forests.

It joined the Commonwealth in June 2022, becoming one of its few members not to have been a British colony.

Twelve soldiers appeared on television early on Wednesday morning, announcing they were cancelling the results of the election and dissolving “all the institutions of the republic”.

The electoral commission had said Mr Bongo had won just under two-thirds of the votes in an election the opposition argued was fraudulent.

The coup leaders added that the country’s borders had been closed “until further notice”.

They said Mr Bongo would be replaced by the head of the presidential guard, Gen Brice Oligui Nguema, and that certain officials would “answer for their actions” following an investigation by the “competent authorities”.

This is the eighth coup in former French colonies in Africa in the past three years.

However, most of the others have been further north, in the Sahel region, where an Islamist insurgency has led to rising complaints that the democratically elected governments were failing to protect the civilian populations.

The French government has condemned the takeover, with a spokesman calling for the election results to be respected.

“France is closely monitoring the development of the situation on the ground,” said Olivier Veran.

Russia and China are among the other countries that have expressed their concern. The European Union’s foreign policy chief said a military takeover would increase instability in Africa.

“This is a big issue for Europe,” said Josep Borrell.

Meanwhile, French mining group Eramet, which employs thousands of people in Gabon, said it had stopped all work in the country for security reasons

The soldiers who announced the coup said they were from the Committee of Transition and the Restoration of Institutions and represent security and defence forces in the country.

One of the soldiers said on TV channel Gabon 24: “We have decided to defend peace by putting an end to the current regime.”

This, he added, was down to “irresponsible, unpredictable governance resulting in a continuing deterioration in social cohesion that risks leading the country into chaos”.

The sounds of loud gunfire could be heard in the country’s capital, Libreville, following the broadcast.

BBC World Service Africa editor Will Ross said this suggested the coup was perhaps not “done and dusted” and there will be some resistance.

A local journalist told BBC Afrique large crowds of people took to the city’s main street to celebrate the takeover, but they were told by the military to go home and move away from strategic areas.

There have also been reports of celebrations in other cities too.

Internet access was suspended following Saturday’s election for security reasons, but was restored shortly after the apparent takeover. A curfew is also in place.

As in previous general elections in Gabon, there were serious concerns about the process in Saturday’s vote.

Main opposition candidate Albert Ondo Ossa complained that many polling stations lacked ballot papers bearing his name, while the coalition he represents said the names of some of those who had withdrawn from the presidential race had still been on the ballot sheet.

Campaign group Reporters Without Borders said foreign media had been banned from setting foot in the country to cover the vote.

Both of Mr Bongo’s previous wins were disputed as fraudulent by opponents. This time, controversial changes were made to voting papers just weeks before election day.

Mr Bongo came to power when his father Omar died in 2009.

In 2018, he suffered a stroke which sidelined him for almost a year and led to calls for him to step aside.

The following year, a failed coup attempt saw mutinying soldiers sent to prison.