On Thursday 22 flights were delayed by up to 20 minutes at Zurich Airport, a spokesperson said, adding that the group could not yet provide figures on the impact of flights on Friday.

The attack began early on Thursday and affected a limited part of Swissport's IT infrastructure, it said in a statement, adding that security teams had detected the attack promptly so that the impact was "largely mitigated".

Most critical systems and applications were not hit, but several servers were affected, which knocked out some systems temporarily.

"The attack has been contained and measures are in place to prevent the further spread. We are now in the process of restoring the affected systems and mitigating the impact on our operation," it said.

(Reporting by Michael Shields; Editing by David Goodman)