TEMPO.CO, Melbourne - Six people have died and five remained on life support after a rare condition known as thunderstorm asthma struck Australia's second-largest city, officials said on Sunday.

The sixth victim died in a hospital on Saturday night from medical complications stemming from a wild thunderstorm that struck Melbourne on Monday night, a Health Department statement said.

Five patients remained in intensive care units and three of those were in critical condition, the statement said. Another 12 patients were in hospitals with less serious respiratory and related conditions.

Monday's storm caused rain-sodden ryegrass pollen grains to explode and disperse over the city, with tiny pollen particles penetrating deep into lungs. Around a third of patients who suffered asthma attacks on Monday reported never having asthma before.

The storm overwhelmed emergency services and hospitals in this city of 4.5 million people, with 8,500 receiving hospital treatment.

The world's first recorded thunderstorm asthma event occurred in Melbourne in 1987, when hospitals reported a five-fold increase in asthma cases. Similar events have happened in the United States, Canada, Britain and Italy. The last major event in Melbourne was in November 2010.

AP