Drones have been seen near military facilities including Denmark's largest, following a series of incidents that caused air disruption earlier this week.
The devices were observed above Karup airbase, among others, forcing it to briefly close its airspace to commercial traffic. Possible sightings were also reported in Germany, Norway and Lithuania.
It is the latest in a string of suspicious drone activity in Denmark, raising concerns about the nation's vulnerability to aerial attack and sparking fears of potential Russian involvement.
Danish authorities said Thursday's incursions appeared to be a hybrid attack, but cautioned that they had no evidence to suggest Moscow was behind it.
Friday's incident took place around 20:15 local time (18:15 GMT) and lasted several hours, duty officer Simon Skelsjaer told news agency AFP.
Though civil airspace above the base was briefly closed, it had no impact because no commercial flights were scheduled in the area at the time, Skelsjaer said.
The other military installations have not been named by Danish state media.
Danish authorities have not speculated as to who might be behind the drone activity.
Some 3,500 people work at Karup airbase, which is home to all of the Danish Armed Forces' helicopters, airspace surveillance and parts of the Danish Defence Command.
The incursions come just days after drones over Danish airports - some of which also housed military facilities - forced airports to shut down and close their airspace.
On Monday, Copenhagen airport closed for several hours after a number of drones were spotted, while possible drone sightings also temporarily shuttered Oslo airport in Norway.
Germany's interior ministry said it was investigating after several drones were spotted over Schleswig-Holstein, the region that borders Jutland, the part of Denmark on the European mainland that is home to Karup airbase and the airports affected by Wednesday's incursions.
Interior Minister Alexander Dobrindt said the threat from drones was high and that Germany would discuss the issue with European partners next month.
Meanwhile, Police in Norway told state media they were investigating possible drone sightings at Orland airbase, to the west of the country, where its F-35 fighter jets are stationed.
There are suspicions that Wednesday's wave of drone incursions may have been part of a Russian strategy of indirect aggression towards NATO states supporting Ukraine in its war with Russia - though this connection has not been proven.
The Russian embassy in Copenhagen has denied absurd speculations of its involvement in what it described as staged provocations.
Danish authorities have not clarified how many drones were involved or the nature of the threats they may pose, leaving many questions unanswered regarding the future of national security in the region.