Australia's east coast battered by cyclone-like storm

A man walks into a strong wind which stripped Sydney's Bondi Beach of tons of sand as heavy winds blow it inland, April 21, 2015.[Photo/Agencies]

Amateur video showed a house in Dungog floating away as floodwaters swept through the town.

"We've got a lot of low-lying houses in the township near rivers and unfortunately a lot of those houses have gone under," Dungog Shire community centre manager Sarah U'Brien told the Australian Broadcasting Corp.

The deluge saw nearly a month's worth of rain dumped on Sydney in 24 hours, data from the Australian Bureau of Meteorology showed.

The NSW State Emergency Service (SES) said it had received more than 3,000 calls for help and had to carry out 19 flood rescues. Three hospitals were without power and had to rely on generators and some 45 schools were closed.

"The consistent gale-force winds ... are actually cyclonic in some areas with gusts up to 135 kilometres per hour," SES Deputy Commissioner Steven Pearce told the ABC.

The destructive storm, which was sitting just off the coast just north of Sydney, whipped up giant seas that closed many beaches, including world-famous Bondi Beach.

The wild weather closed Sydney Harbour to commercial shipping, forcing a cruise ship with some 2,500 passengers to wait off the coast, battered by big swells.