A child's helium balloon has been blamed for a power failure that knocked out Greece's main civil aviation radar and snarled flights for over an hour over the weekend, a report said on Monday.

Top-selling Ta Nea daily said the balloon knocked out the "heart" of the Athens flight information region (FIR) radar that oversees Greek airspace.

Officials at Greece's civil aviation authority and the electricity distribution network confirmed the problem but declined to comment on the report.

The civil aviation authority YPA said the radar controlling the Athens and Macedonia region had sustained a "loss of image" around midday on Saturday for over an hour due to an electrical failure that followed a power outage.

And a source at state electricity distributors DEDIE said that an "aluminised" helium balloon had caused a 13-minute power failure in the area near YPA's headquarters in southern Athens, some 40 minutes before the radar shutdown.

YPA insisted that aviation safety was not impaired for the duration of the power failure though delays in takeoff and landings were caused.

"Traffic controllers here remained in radio communication with the aircraft and radar remained operational at Athens International Airport and regional airports," a civil aviation source told AFP.

A committee was formed to investigate the causes of the malfunction.

[Image via Agence France-Presse]