The authorities in Equatorial Guinea say they thwarted an attempted coup in late December.
At least 30 armed men were arrested recently in Cameroon, near the border with Equatorial Guinea.
Security Minister Nicholas Obama Nchama said radical opposition parties had recruited mercenaries to overthrow the government of President Teodoro Obiang Nguema, who has been in power for nearly 40 years.
He said the coup attempt had been foiled with the help of the Cameroonian security services.
The alleged mercenaries – from Chad, Cameroon and the Central African Republic (CAR) – were found with rocket launchers, rifles and large amounts of ammunition.
Mr Obiang’s government is often accused of corruption and human rights abuses.
An infamous failed coup attempt was led 14 years ago by former British soldier Simon Mann.
The former commando and businessman was arrested in Zimbabwe in 2004 and extradited four years later to Equatorial Guinea, where he was sentenced to 34 years in prison.
One year later he was released after being pardoned by Mr Obiang.