COPENHAGEN, Denmark (AFP) — More drones were observed over Danish military sites overnight for the second straight day, Denmark’s army said Sunday, the latest in a string of sightings across the country over the past week.

“The Armed Forces can confirm that drones have been observed at several of the Armed Forces’ locations during the night. Several capacities were deployed,” the military said in a statement.

It provided no other details about the incidents or the military’s response.

Danish media reported that no airports had been closed overnight.

Mysterious drone sightings across Denmark and Norway since 22 September have prompted the closure of several airports, with Denmark hinting at possible Russian involvement.

On Saturday, Denmark’s military said unidentified drones had been observed over “several military sites” overnight Friday to Saturday, but refused to disclose any other details.

Police did confirm that “one to two drones” had been observed on Friday evening near and over the Karup military base, the country’s biggest base which houses all of the armed forces’ helicopters, airspace surveillance, flight school and support functions.

The North Atlantic Treaty Organization has “enhanced vigilance” in the Baltic following the intrusions, a spokesperson for the defense alliance said.

The reinforced measures “include multiple intelligence, surveillance and reconnaissance platforms and at least one air-defense frigate” in the region to the west of Russia, Martin O’Donnell told a press conference overnight Saturday to Sunday.