Flights into Sydney, Australia, were disrupted earlier by an outback dust storm that dramatically reduced visibility in the area and raised health fears.

The dust blacked out the Australian mining town of Broken Hill yesterday, forcing one mine to shut down, and then swept east, shrouding Sydney in a red glow this morning.

View pictures of the dust storm

International flights had to be diverted from Sydney, ferries on Sydney Harbour were suspended and motorists were warned to take care on roads as visibility was dramatically reduced.

Health authorities had urged people with asthma or breathing difficulties to stay indoors.

The dust set off smoke alarms in some buildings in Sydney's central business district.

The Bureau of Meteorology said a major cold front in New South Wales state caused severe thunderstorms and gale-force winds, which whipped up the dust from the drought-stricken inland and spread it across Australia's most populous state.

The 100km/h winds also fanned bushfires in the state.

'This is unprecedented. We are seeing earth, wind and fire together,' said Dick Whitaker from The Weather Channel earlier today.

Australia is the driest inhabited continent on earth. The NSW state government recently cut the state's 2009/10 wheat crop estimate by 20% because of hot, dry weather across the grain belt.

The country is one of the most vulnerable nations to climate change, but also the world's biggest greenhouse gas emitter per capita as it relies on coal-fired power stations for the bulk of its electricity.