Army officers in Gabon have gone on national television to declare that they had taken power.
They proclaimed the results of Saturday’s election, in which President Ali Bongo was declared the winner, null and void.
According to the electoral commission, Mr Bongo received slightly under two-thirds of the vote in an election that the opposition claimed was rigged.
His demise would end his family’s 53-year reign in Gabon.
Gabon is one of Africa’s biggest oil producers, yet forests cover approximately 90% of the country.
Twelve soldiers appeared on television early Wednesday morning, declaring that the election results would be annulled and “all the institutions of the republic” would be dissolved.
They also stated that the country’s borders were blocked “until further notice.”
This would be the eighth coup in former French colonies in Africa in the last three years, if confirmed.
The majority of the others, though, have been further north in the Sahel area, where an Islamist insurgency has led to growing concerns that democratically elected governments are failing to safeguard civilian populations.
French Prime Minister Elisabeth Borne said her country was closely monitoring the situation, while the European Union’s foreign policy head warned that a military takeover would exacerbate Africa’s instability.
“This is a big issue for Europe,” said Josep Borrell.
Meanwhile, the French mining company Eramet, which employs thousands of people in Gabon, announced that it had halted all operations in the nation for security reasons.
The soldiers who proclaimed the apparent coup claimed to be from the Committee of Transition and Institutional Restoration and to represent the country’s security and defense forces.
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 th,at risks leading the country into chaos”.
Following the broadcast, the sounds of gunshots could be heard in the country’s capital, Libreville.