The European Commission said Bulgarian authorities suspected the disruption "was due to blatant interference" from Moscow but it was not clear if the chartered flight was deliberately targeted.

"We can indeed confirm that there was GPS jamming," Commission spokeswoman Arianna Podesta told a press conference in Brussels.

The aircraft landed safely at Plovdiv International Airport, in the south of the country, without having to change route.

Commission president Von der Leyen, 66, was in Bulgaria as part of a seven-country tour of "frontline" European Union states which, sitting on the 27-nation bloc's eastern flank, are more exposed to Russian hybrid threats.

The region has experienced "a lot of such jamming and spoofing activities", the commission said, adding it has sanctioned several companies believed to be involved.

The Bulgarian government confirmed the incident.

"During the flight carrying European Commission president Ursula von der Leyen to Plovdiv, the satellite signal transmitting information to the plane's GPS navigation system was neutralised," a government statement said.

"To ensure the flight's safety, air control services immediately offered an alternative landing method using terrestrial navigation tools," it said.

The Financial Times newspaper, which first reported the incident, said the plane was forced to land using paper maps.