“Most of the leaders have been arrested,” Bio said in a televised address. “The attackers are being repelled by a combined team of security forces and police. Calm has been restored.”

Sierra Leone imposed a nationwide curfew in the hunt for the assailants, who also invaded the country’s prisons and released inmates while taking some hostages.

“The prisoners are now on the run,” Issa Bangura, a spokesman for the army, said by phone.

The central prison and the special court prison where the most serious offenders are held were broken into, Bangura said. One assailant was killed and three soldiers were critically injured, he said.

The developments in Sierra Leone come after military takeovers in Gabon and Niger this year and others in Mali, Guinea, Burkina Faso and Chad over the past three years. The July putsch in Niger, which the Economic Community of West African States is currently negotiating to overturn, created a belt of military-run countries stretching from the Atlantic Ocean to the Red Sea.

“We shall continue to protect the peace and security of Sierra Leone against the forces that wish to truncate our much-cherished stability,” Bio said.

The aggression was a plot by “certain individuals” to acquire arms and disturb the peace and constitutional order in the country, the regional bloc known by its acronym Ecowas, said in a statement. “Ecowas condemns this act and calls for the arrest and prosecution of all participants in this illegal act.”

The disturbances disrupted flights on Sunday, the West African nation’s civil aviation agency said in a statement. It told airlines to reschedule departing flights after the curfew is lifted.

Bio, 59, won a second mandate to lead Sierra Leone earlier this year. The results were rejected by the opposition and questioned by international observers including the US, which raised concerns about “irregularities” in the election results.

The military headquarters lies strategically near the presidential palace.

Bio, a retired military officer, briefly led a military junta during an 11-year civil war that ended in 2002. The June election was the fifth since the end of civil war, which claimed 50,000 lives and devastated the economy.