Around 1,400 passengers were grounded at Warsaw's Frederic Chopin airport Sunday, after hackers attacked ground computer systems used to issue flight plans.

A spokesman for state-run airline LOT, Adrian Kubicki, said the problem was fixed after around five hours, but that 10 of the carrier's domestic and international flights had to be cancelled. About a dozen more were delayed.

"We're using state-of-the-art computer systems, so this could potentially be a threat to others in the industry," he said, adding that the safety of ongoing flights had not been compromised.

The affected flights were bound for Hamburg, Düsseldorf, Copenhagen and domestic destinations.

LOT said some passengers had since been able to board their flights, but that the remainder had been put up in hotels on Sunday evening.

nm/cmk (Reuters, AP)