The Danish defense ministry said Saturday that “drones have been observed at several of Danish defense facilities.” The new drone sightings overnight Friday into Saturday come after there were several drone sightings in the Nordic country earlier this week,

Danish Prime Minister Mette Frederiksen said Tuesday that she considered the initial drone intrusions over Copenhagen and elsewhere to be "a serious attack against critical infrastructure in Denmark."

Denmark said drones that halted flights at its main airport on Monday were the most serious attack yet on its critical infrastructure and linked them to a series of suspected Russian drone incursions and other disruptions across Europe.

The incidents come as Russian drones and military aircraft have increasingly entered NATO airspace, prompting heightened alert and readiness across the alliance.

European governments are on alert after Russian incursions into NATO airspace, but the Danish authorities said they could not say who was behind the latest incidents.

The vessel had its tracking equipment deactivated, indicating the vessel wished to avoid detection by Danish authorities.

Denmark's defense chief has called a series of unidentified drones being spotted near airports and military installations a "hybrid attack."

Denmark reported the latest in a series of drone sightings on Saturday, with the most recent incident occurring near military installations.

Danish defense minister Troels Lund Poulsen said a recent wave of disruptive drone flights near the NATO ally's airports and military installations are a "hybrid attack" and Denmark was considering activating NATO's Article 4 in response.