By Laura Sharman, CNN

(CNN) — Denmark has temporarily banned civil drone flights in its airspace as it prepares to host a top European Union meeting on defense and the war in Ukraine, and after a surge of suspicious drone activity at several airports and military sites last week.

The ban, which runs from Monday to Friday, aims to eliminate any risk of “hostile” drones being mistaken for legal ones or vice versa, the country’s transport minister Thomas Danielson told CNN.

Several unexplained sightingsof drones over civilian airports and a military base were reported in Denmark last week. The incidents forced several airports to temporarily close and disrupted travel for tens of thousands of people.

Top European leaders will descend on Copenhagen on Wednesday for a European Council meeting to discuss defense and Ukraine, followed by a European Political Community summit in the city the next day.

“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,” Danish Defense Minister Troels Lund Poulsen said in a statement on Sunday.

Europe has been on high alert in recent weeks due to a string of drone sightings, as well as incursions by Russian drones into NATO airspace over Poland and Romania and the violation of Estonian airspace by Russian fighter jets.

Danish Prime Minister Mette Frederiksen said that while authorities cannot conclude who is behind the drone sightings, “we can at least conclude that there is primarily one country that poses a threat to Europe’s security – and that is Russia.” The Kremlin has denied involvement in the drone sightings as well as that it violated Estonian airspace.

On Monday, Romanian Defense Minister Ionut Mosteanu said that another drone had been found close to his country’s border with Ukraine, weeks after Bucharest alleged that a Russian drone breached its airspace during an attack on its neighbor.

“We just found another drone, another Russian drone that fell down on our territory in the Danube Delta,” Mosteanu told a panel at the Warsaw Security Forum. “And this is a common thing for the last three and a half years,” he said.

NATO responds

In response to the unexplained drone flights in Denmark, NATO said on Saturday that it is upgrading defense measures in the Baltic Sea region.

The following day, FSG Hamburg, a German air defense frigate with NATO’s “Baltic Sentry” mission, arrived in Copenhagen to help strengthen airspace surveillance during the upcoming EU summit, the Danish defense ministry said in a statement to the Associated Press.

The “Baltic Sentry” mission launched in January in response to a string of incidents that damaged power cables, telecom links and gas pipelines on the Baltic Sea bed.

It is now joined by the newly launched “Eastern Sentry” mission which aims to bolster defenses on Europe’s eastern flank following Russian drone incursions into Polish airspace.

Additionally, Germany announced it will provide “Counter-small Unmanned Aircraft Systems” at Denmark’s request to detect drones using radar, optical and acoustic technology, according to the Associated Press.

France’s armed forces said Monday that it has deployed a temporary joint task force to Denmark in response to the drones in the country’s airspace, comprised of 35 personnel, a Fennec helicopter and anti-drone facilities.

“This task force reinforces the Danish and European assets already deployed, underscoring European solidarity in defense against a serious threat,” the armed forces said in a statement.

Sweden has also pledged to lend Denmark an anti-drone system, though details remain undisclosed, the AP said.