Disruptions which affected several European airports over the weekend were caused by a third-party ransomware incident, the European Union's cybersecurity agency said on Monday.

"The type of ransomware has been identified. Law enforcement is involved to investigate," the agency ENISA said in a statement.

Operations at several major airports in Europe faced disruptions Saturday after a cyberattack targeted the service provider for check-in and boarding systems.

On Monday, operations remained disrupted at the Berlin airport, with runners in town for the Berlin Marathon among those affected.

Hundreds of flights affected

On Saturday evening, Brussels Airport said Sunday flights will also be affected.

"Brussels Airport has asked airlines to cancel half of the scheduled departing flights on Sunday 21 September in order to avoid long queues and late cancellations," a spokesperson for the Belgian airport said.

The airport authorities also advised the passengers with a flight scheduled for Saturday to confirm their travel with airlines before heading to the airport.

Flights were delayed or canceled at airports in London, Berlin and Brussels.

"There was a cyberattack on Friday night, 19 September, against the service provider for the check-in and boarding systems, affecting several European airports, including Brussels Airport," a statement shared on the website of Brussels Airport said.

"This has a large impact on the flight schedule and will, unfortunately, cause delays and cancellations of flights," the operator said.

"The service provider is actively working on the issue and trying to resolve the problem as quickly as possible."

According to aviation data provider Cirium, 29 departures and arrivals have been canceled so far at Heathrow, Berlin, and Brussels. A total of 651 departures were scheduled from Heathrow on Saturday, along with 228 from Brussels and 226 from Berlin.

Service provider reports 'cyber-related disruption'

Meanwhile, airport service provider Collins Aerospace confirmed to AFP that multiple European airports, including those in Brussels, Berlin, and London (Heathrow), were hit by "cyber-related disruption," which affected the check-in and baggage drop systems.

"We have become aware of a cyber-related disruption to our MUSE software in select airports," the aerospace firm said.

It added that the impact is "limited to electronic customer check-in and baggage drop and can be mitigated with manual check-in operations."

More airports in Europe report issues

Heathrow also warned of delays caused by "a technical issue" at a third-party supplier.

Meanwhile, Berlin's Brandenburg Airport ran a banner on its website saying, "Due to a technical issue at a system provider operating across Europe, there are longer waiting times at check-in. We are working on a quick solution."

Later, Dublin Airport announced that it was also facing a minor impact from the issue.

Saturday's apparent cyberattack comes a day after the airport in Russia's second-largest city, St. Petersburg, said that its website had been hacked.

Edited by: Karl Sexton, Dmytro Hubenko