PARIS — The French navy opened fire at drones that were detected over a highly-sensitive military site harboring French nuclear submarines, according to newswire Agence France-Presse.

Five drones were detected Thursday night over the submarine base of Île Longue, in Brittany, western France, a strategic military site home to ballistic missile submarines, the AFP reported, citing the the French gendarmerie, which is part of the military. The submarines harbored at the base carry nuclear weapons and are a key part of France’s nuclear deterrent.

French navy troops in charge of protecting the base opened fire, the report said. It was unclear whether the drones were shot down.

Drones had already been spotted in the area last month, albeit not directly above the base, per reports in French media. The site had been buzzed by drones long before the invasion of Ukraine.

The incident follows a string of recent drone incursions in NATO airspace, with unmanned aircrafts seen buzzing around sensitive military sites and civil infrastructures in recent months across Europe, including in Belgium, Germany, Denmark and Norway.

In Poland, fighter jets were scrambled in September to shoot down drones of Russian origin, an incident widely seen as an escalation of Russian President Vladimir Putin’s hybrid war on Europe.

French authorities haven’t yet commented on the suspected origin of the drone incident Thursday at the well-known military site.