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.
The electoral commission said Mr Bongo had won just under two-thirds of the votes in an election the opposition argued was fraudulent.
His overthrow would end his family’s 56-year hold on power in Gabon.
Twelve soldiers appeared on television announcing they were cancelling the results of the election and dissolving “all the institutions of the republic”.
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”.
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.