Around 75 soldiers, a warship and other military capabilities are being sent to Denmark to bolster the country's aerial defences ahead of two summits in Copenhagen this week.

More drones have been spotted in the airspaces of Denmark and Lithuania, stoking security concerns and fears amid suspected growing Russian aggression.

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

More drones spotted in Denmark over military sites as Nato vows to ramp up vigilance - Dozens have been injured in a sustained attack on Kyiv and other parts of Ukraine by Russia

Danish Prime Minister Mette Frederiksen called it “the most serious attack on Danish critical infrastructure to date.”

Denmark reported to NATO allies that unspecified "state actors" were responsible for drone incursions that shut two airports, Latvia's foreign minister told Reuters on Thursday, but Danish officials said it was still unclear who was behind the incidents.

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

Denmark is probing potential Russian involvement after enduring the second drone attack this week as authorities are bracing for the possibility of more incidents. Large professional drones spotted at several airports and military air bases in Denmark disrupted flights and sparked a major police operation overnight.

Denmark’s Prime Minister Mette Frederiksen warned Danes to brace for more hybrid attacks, pointing to Russia as Europe’s main security threat, just before a suspected drone sighting disrupted air traffic in Denmark for the third time in a week.

Right now, though, U.S. leadership appears reticent. Coincidentally or not, the serious airspace violations have happened since Trump’s summit with President Vladimir Putin in Alaska in August, when the U.S. leader dropped his demand for a ceasefire in Ukraine.