Factbox-Russia's suspected 'hybrid war' puts European air defences to the test

BRUSSELS (Reuters) -Russia's drone incursions and airspace violation of European NATO countries has increased since September, when more than 20 Russian drones entered Polish airspace and three Russian military jets violated Estonia's airspace for 12 minutes.

Since then, many drone flights, the origin of which are mostly unknown, have disrupted airspace operations in Europe.

European Commission President Ursula von der Leyen has called the incursions "hybrid warfare", and while she has not said Russia was responsible for all the incidents, she said it was clear Russia's aim was to "sow division" in Europe.

Below are some of the biggest airspace violations and drone sightings reported so far this year:

BELGIUM

The Brussels and Liege airports were closed on Tuesday evening after drones were spotted, diverting many incoming planes and preventing others from taking off. The Brussels airport reopened Wednesday morning though some flights were cancelled and others delayed.

Belgian Defence Minister Theo Francken said on Sunday that police was investigating drone sightings over the Kleine Brogel air base in north-east Belgium.

The country opened an investigation last week after two drone sightings over a military base in the country's south-east, and another inquiry last month after several drones were spotted flying over a military base at Elsenborn, on the German border.

CZECH REPUBLIC

The Czech army said on September 10 it was detecting an increasing number of unidentified drones flying over its military facilities, according to the Institute for the Study of War research group.

DENMARK

Drones disrupted air traffic at six Danish airports in September, including in Copenhagen, the Nordic region's busiest airport, in what Prime Minister Mette Frederiksen called a hybrid attack on her nation.

ESTONIA

Three Russian military jets violated NATO member Estonia's airspace for 12 minutes on September 19, before NATO Italian fighter jets escorted them out.

GERMANY

The Berlin and Bremen airports briefly closed on the weekend after two separate drone sightings, local media reported.

Drones were spotted at airports and military installations across Germany earlier in October, Bild newspaper quoted a confidential police report as saying, suggesting sightings at Munich Airport on October 3 were the tip of the iceberg.

The interior ministry of the German state of Schleswig-Holstein said on September 26 that drones had been sighted overnight and they were being investigated for possible espionage and sabotage.

LITHUANIA

NATO member Lithuania closed Vilnius Airport and Belarus border crossings on October 28, after several objects, identified as likely helium balloons, entered its airspace, the National Crisis Management Centre said, the fourth such incident in a week.

The country said on October 23 that two Russian military aircraft had entered its airspace for about 18 seconds, prompting a formal protest and a reaction from NATO forces, while Russia denied the incident.

NORWAY

Norway's Oslo Airport temporarily paused one or several landings early on October 6 after a report of a drone sighting near the airport, its operator Avinor said.

POLAND

Polish MiG-29 fighter aircraft intercepted a Russian reconnaissance plane over the Baltic Sea on October 30, Polish Defence Minister Wladyslaw Kosiniak-Kamysz said.

The country's army said that its jets had intercepted a Russian aircraft flying a reconnaissance mission in international airspace over the Baltic Sea on October 28.

Some 20 Russian drones entered the country's airspace on the night of September 9-10. NATO deployed F-35 and F-16 fighter jets, helicopters and a Patriot air defence system to respond to the incursion.

ROMANIA

Romania scrambled fighter jets on September 13, when a drone breached the country's airspace during a Russian attack on Ukrainian infrastructure near the border, the defence ministry said.

SPAIN

Flight operations at Palma de Mallorca Airport were temporarily suspended on October 20 following drone sightings, according to the ISW.

(Reporting by Alessandro Parodi, editing by Inti Landauro and Michael Perry)