Seven passengers were injured when a Qantas plane was hit by severe turbulence over Malaysia and suffered a rapid loss of altitude.

The Airbus A330 with 219 passengers and crew aboard was flying from Hong Kong to the Australian west coast city of Perth when the incident happened.

It comes just a few weeks after an Air France Airbus crashed in the sea of the cost of Brazil with the loss of 228 lives.

Passengers on the Qantas flight described the panic and confusion in the darkened cabin as passengers not wearing seat belts were hurled from their seats.

One passenger said the jet suddenly lost altitude and dropped the height of a 30-storey building.

"All of a sudden the plane dropped, I reckon about a 30-storey building. It just sort of dropped straight down and there was a hell of a kerfuffle commotion in the plane," he said.

"There was a little bit of turbulence first and then there was quite a large drop and I think a few people went flying around."

Six passengers and a crew member were treated for minor injuries on board as the airliner continued to Perth, Qantas corporate affairs manager David Epstein said.

He added: "The turbulence was very severe, it only lasted 15 to 20 seconds, but it was enough, clearly, to injure these six passengers and one crew member.

"But the aircraft continued to operate normally and our captain, who's a veteran of the airline for about 21 years, after we'd made some medical checks and contacted our medical services provider, felt it was perfectly okay to continue flying onto Perth."

Australian government safety officials are investigating the incident.

Qantas said there was no reason to link the incident to other recent in-flight incidents involving A330 aircraft.

A computer malfunction on a Qantas A330 flying from Singapore to Perth on October 7, 2008 caused the jet to nose-dive twice, leaving 12 passengers and crew seriously injured.

The Australian airline underwent a safety review last year after a series of problems, including an oxygen tank explosion on a Boeing 747-400 that ripped a hole in the jet's fuselage last July, forcing it to make an emergency landing in the Philippines. No one was injured.

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