Sierra Leone’s military is hunting for leaders of an attack on an army base in the capital over the weekend, as the authorities tighten security in the city, according to Bloomberg.

Assailants attacked a military barracks in the north of Freetown in the early hours of Sunday morning, before invading two prisons and freeing an unspecified number of inmates. The unrest comes amid increasing tension in the West African nation after President Julius Maada Bio’s disputed reelection in June.

The security forces arrested several perpetrators on Sunday and calm was restored to the city, Bio said in a televised address. Some of the group’s leaders fled to the hills on the outskirts of Freetown, where authorities are working to capture them, Information Minister Chernor Bah said on Monday.

“They have been surrounded and we are very confident that they will be apprehended the next day or so,” he said. “We’re reviewing everything that happened to understand why this breach happened. The President has instructed that additional security measures are put in place.”

The developments in Sierra Leone come after military takeovers in Gabon and Niger this year, and coups 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 African nations that stretches from the Atlantic Ocean to the Red Sea.

The military headquarters lies strategically near the presidential palace and some of the attackers have been identified as former and present and security forces, according to Bah. A night curfew will remain in place for the time being, while the authorities work to determine whether the weekend’s events amount to an attempted putsch, he said.

“We want to make sure that threshold for an attempted coup is met before signifying it as such,” he said. “Once we have it, we will have to try the people who’ve been arrested.”

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 for after the curfew is lifted.

At least one attacker was killed and three soldiers were injured in the raids on the city’s prisons, Issa Bangura, a spokesman for the army, said by phone. “The prisoners are now on the run,” he said.

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.

A retired military officer, Bio 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 the war, which claimed 50,000 lives and devastated the economy.

Sierra Leone became sub-Saharan Africa’s fastest-growing economy in 2012, when iron ore took over from diamonds as its biggest export.