Denmark ordered a ban on Sunday on civil drone flights, after drones were observed at several military facilities overnight, following a week in which drone sorties caused the temporary closures of several Danish airports.

The Danish military said in a statement it had deployed "several capacities" in response to the overnight sightings at bases, declining further comment on the nature of its response.

Drone sorties earlier this week forced Denmark to shut airports, including a nearly four-hour closure of Copenhagen Airport on Monday.

Denmark has called the drones part of a "hybrid attack." It has stopped short of saying definitively who it believes is responsible, but Prime Minister Mette Frederiksen has suggested it could be Moscow, calling Russia the primary "country that poses a threat to European security." The Kremlin denies blame.

Under the ban, civilian drones will be barred from Danish airspace from Monday through Friday of the coming week, when Denmark, which holds the rotating presidency of the EU for the second half of this year, will be hosting European leaders.

"We are currently in a difficult security situation, and we must ensure the best possible working conditions for the armed forces and the police when they are responsible for security during the EU summit," Defence Minister Troels Lund Poulsen said in a statement on Sunday.

Denmark will host EU leaders on Wednesday, followed by a summit on Thursday of the wider, 47-member European Political Community, set up to unite the EU with other friendly European countries after Russia's 2022 invasion of Ukraine.

A German air defense frigate arrived in Copenhagen on Sunday to assist with airspace surveillance during the high-profile events.