The Maghreb Freedom Flotilla, part of an initiative to break Israel’s blockade of Gaza, announced Sunday that it has raised its security alert level after three unidentified drones were spotted over one of its vessels.

In a statement on Facebook, the flotilla said the crew of the ship Mali/Deir Yassin detected the drones, adding that one of them flew dangerously close to the vessel.

The flotilla described the incident as a “worrying development” that prompted heightened vigilance, without providing further details about the drones’ origin or identity.