NATO has said it is upgrading its mission in the Baltic Sea with an air-defence frigate and other assets in response to drone incursions in Denmark.
Unidentified drones were observed near military installations in Denmark overnight, the Armed Forces said, following several drone incursions near airports and critical infrastructure this week.
Police said "one to two drones" were observed yesterday at around 8.15pm local time 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.
Copenhagen Airport, the Nordic region's busiest, closed for several hours late on Monday as several large drones were seen in its airspace.
Five smaller Danish airports, both civilian and military, were also shut temporarily in the following days.
Danish Prime Minister Mette Frederiksen said on Thursday that "over recent days, Denmark has been the victim of hybrid attacks," referring to unconventional warfare.
Investigators have so far failed to identify those responsible, but Danish Defence Minister Troels Lund Poulsen said that the flights appeared to be "the work of a professional actor".
Ms Frederiksen has pointed the finger at Russia.
"There is one main country that poses a threat to Europe's security, and it is Russia."
Russia said it "firmly rejects" any suggestion that it was involved in the Danish incidents.
Its embassy in Copenhagen called them "a staged provocation", in a post on social media.
In response, NATO will "conduct even more enhanced vigilance with new multi-domain assets in the Baltic Sea region", it said in a statement.
The alliance said the new assets included "intelligence, surveillance, and reconnaissance platforms and at least one air-defence frigate".
A NATO spokesperson said they would not provide details on which countries were contributing the extra assets.
The new assets will enhance NATO's "Baltic Sentry" mission, launched in January in response to a string of incidents in which power cables, telecom links and gas pipelines on the Baltic Sea bottom have been damaged.
NATO countries have deployed frigates, patrol aircraft and naval drones as part of the mission, to help protect critical infrastructure.
The alliance also launched the "Eastern Sentry" mission this month, to bolster the defence of Europe's eastern flank in response to Russian drone incursions into Polish airspace.
Drone reports also closed Oslo airport in Norway for several hours earlier in the week, following drone incursions in Polish and Romanian territory and the violation of Estonian airspace by Russian fighter jets, which raised tensions in light of Russia's ongoing invasion of Ukraine.
NATO warned Russia on Tuesday that it would use "all necessary military and non-military tools" to defend itself after Estonia said that three Russian MiG-31 fighter jets violated its airspace for 12 minutes before NATO Italian fighter jets escorted them out.
Russia has disputed that Russian jets violated Estonia's airspace and said that its drones had not planned to hit targets in Poland.
German Interior Minister Alexander Dobrindt said on Saturday that the threat from drones was "high" and that the country would take measures to defend itself.
Russia's Foreign Minister Sergei Lavrov warned NATO and the European Union on Saturday that "any aggression against my country will be met with a decisive response".
