SYDNEY - QANTAS on Monday defended its fleet of Airbus A330s after severe turbulence left 12 people injured in the latest scare involving the aircraft.

The Australian flag-carrier blamed the incident during a flight from Hong Kong to Perth on freak weather conditions and dismissed any link to other A330 accidents including the Air France disaster on June 1.

'There is nothing to link the aircraft to anything untoward,' said company spokesman David Epstein.

Flight QF68 was passing over Malaysia about four hours into its flight when it was hit by a blast of ferocious turbulence, dropping about 30 metres and sending passengers flying.

'It appeared like we'd just dropped out of a 30-storey building,' said passenger Keith Huxtable, as another traveller described how a woman was flung into the plane's ceiling.

'I was sitting at the exit door and I had this lady, (who) was waiting at the restroom and she flew up and hit the ceiling and came crashing down to the floor,' the passenger, named John, told Fairfax radio. 'It was just a matter of a few seconds but it was really sudden and things went flying.'

Twelve people were treated for bruises and neck and back pain after the plane landed at about 7.30am on Monday (Singapore time) in Perth, AAP news agency said.

The incident comes just 11 days after a cockpit blaze forced a Jetstar A330 to make an emergency landing, and also follows the Air France tragedy when 228 died in a mysterious accident involving the same model of plane. Last October, a Qantas A330 went into two steep dives over Western Australia, causing several serious injuries and prompting an emergency landing.

Qantas, which has 10 A330-300s and six Airbus A330-200s and also operates budget airline Jetstar, dismissed any links between Monday's incident and previous ones.

'There is no reason to link the incident to other recent in-flight incidents involving A330 aircraft,' Qantas said in a statement, adding an investigation was under way. -- AFP