An airport in Denmark has been forced to close after drones were spotted nearby, local police have said.

Incoming and departing flights from Aalborg Airport were halted following the incident on Wednesday night.

In a post on X, Nordjyllands Police said: “Drones have been observed near Aalborg Airport and the airspace is closed. The police are present and investigating further.”

The force said more than one drone was sighted in the airport’s airspace, adding that it was not known if they were the same ones that affected Copenhagen Airport earlier this week.

It said the purpose of the drones was unknown, and it was not clear who was controlling them, but they were flying with their lights on.

Four flights were impacted, including two SAS planes, one Norwegian and one KLM flight, a spokesperson for the airport said.

Aalborg is located in the north of the country, in the Jutland region, and is Denmark’s fourth-largest city by population.

Denmark’s national police said it was receiving notices of drones in other parts of the country. It said the Danish Armed Forces were also affected as they use Aalborg Airport as a military base.

The previous incident at Copenhagen Airport was described by the government as the most serious attack yet on its critical infrastructure and linked the drones to a series of suspected Russian drone incursions and other disruptions across Europe.

Authorities in Norway also shut the airspace at Oslo airport for three hours after a drone was seen there.

Denmark‘s prime minister later said she “cannot deny” that drones seen over the airport were flown by Russia.

Authorities in Norway and Denmark are in close contact over the incidents in Copenhagen and Oslo, but their investigation has not yet established a connection, Norway’s foreign minister said on Wednesday.

It also comes after disruption at Heathrow Airport last week following a cyber attack that also hit other major airports in Europe.