Sydney has been covered in a spectacular cloud of red mist caused by a massive dust storm from the Outback.

The harbour bridge and opera house were barely visible while flights had to be suspended or diverted as the airport was closed. Harbour ferries were tied up as winds reached 60mph.

Residents awoke yesterday to a crimson dawn, with some fearing a massive bush fire was on their doorstep. People headed to work wearing breathing masks, while hospitals reported a sharp increase in patients with breathing difficulties.

The worst dust storm in 70 years extended from an area south of Sydney, Australia's largest city, to Brisbane, more than 500 miles north.

More pictures: Sydney's red dawn

“It's just red, red, red as far as you can see,” one caller told Radio 2GB. “I've not seen anything like this before.”

High overnight winds had carried a cloud of thick dust at a rate of 60,000 tons an hour from the remote Northern Territory across New South Wales.

Bureau of Meteorology senior forecaster Jane Golding said the fiery haze was the result of the sun hitting the dust blanket. “The reason for the dust is we had some really strong winds in the inland areas of New South Wales and in South Australia for a sustained period yesterday,” she said.

“That's lifted a whole lot of dust off the ground because it's quite dry out there, many of those areas are still drought affected.”

Many areas had experienced dramatic weather, from unseasonably warm temperatures to torrential rain and hail storms. The Bureau of Meteorology has issued a severe weather warning for damaging winds in Sydney.

“It did feel like Armageddon because when I was in the kitchen looking out the skylight, there was this red glow coming through,” Sydney resident Karen told Australian Broadcasting Corp. radio.

The storms - visible as a huge brown smudge in satellite photographs of Australia - were the most severe since the 1940s, experts said.

“These dust storms are some of the largest in the last 70 years,” said Nigel Tapper, an environmental scientist at Monash University. He said that one blew as far as New Zealand, 1,400 miles away.

Motoring authorities issued a warning urging drivers to exercise caution and reduce speed due to “significant dust over the city affecting visibility”. Traffic queued bumper to bumper.

The State Emergency Service received nearly 200 requests for assistance following reports of damage to roofs and trees being blown down.

Hail stones as big as cricket balls hit the town of Crookwell, damaging windows and tiles. The New South Wales Fire Brigades received more than 500 calls between 3am and 7am, triggered by automatic fire alarms. It normally receives 30 in that period.

“This is one for the books,” a spokesman said. “A lot of fire alarms are particle-type alarms and the dust gets in and sets them off. Some people feared half of Sydney was engulfed in a huge bushfire."

More pictures: Sydney's red dawn