Gunmen launched an attack on the main airport in Niger’s capital, early Thursday, triggering a firefight and a series of explosions, according to witnesses and a security official.

The official said security forces were deployed after the attackers breached airport defenses, although the identities of the gunmen were not immediately known. The official spoke on condition of anonymity because they were not authorized to comment publicly.

In the aftermath of the attack, soldiers were seen conducting searches of people traveling along roads leading to the airport, an Associated Press journalist reported.

The incident marks the second attack on Niamey’s Diori Hamani International Airport this year. In January, the Islamic State group claimed responsibility for a similar assault that targeted Niger’s drone infrastructure.

Niamey’s Diori Hamani International Airport is a key strategic facility, housing a Nigerian air force base and serving as the headquarters of the joint military force formed by Niger, Burkina Faso, and Mali.

Although security at the airport was strengthened following the January attack, analysts warn that jihadist groups in Niger and across the wider Sahel remain a significant threat.