LONDON/BRUSSELS -- A cyberattack targeting the service provider for the check-in and boarding systems has disrupted operations at several major European airports, causing flight delays and cancellations.

Heathrow Airport, the primary and largest international airport serving London, said on Saturday morning that "a technical issue" affected a service provider for check-in and boarding systems.

"A third-party supplier providing check-in and boarding systems for several airlines across multiple airports is experiencing a technical issue, which may cause delays for departing passengers," a Heathrow Airport spokesperson was quoted as saying by local media.

Airports in Brussels and Berlin were also affected by the attack.

Brussels Airport said in a statement that the attack on Friday night has forced the airport to only use manual check-in and boarding as the service provider is working on solutions to the problem.

The problem caused major delays and cancellations of flights on Saturday. According to the flight traffic information provider Flightradar24, as of Saturday morning, approximately 91 percent of the flights at Brussels Airport are delayed, with an average delay time of 51 minutes.

Germany's Berlin Brandenburg Airport said it was also affected, warning passengers to expect longer waiting time for check-in and boarding.