Australia's New South Wales (NSW) Premier Kristina Keneally on Monday declared four more areas in the state as natural disaster zones, bringing the total number of areas to 37 since the floods began on November 29.

The latest natural disaster areas including Goulburn, Mulwaree, Cowra, Coolamon and Tamworth local government areas, have reported significant public infrastructure damage due to flooding and heavy rainfall.

Roads, drainage, causeways, sewerage and wastewater treatment works, buildings and dams in the areas have been affected.

Keneally said, "This has been the most widespread flooding event of this kind NSW has experienced in more than 30 years."

The premier also drew attention to the fact that there are still 4,600 people remaining isolated, with the prospect of more rain to come in the weeks and months ahead, and some areas still under evacuation alert.

The State Emergency Service said it has received 2,755 requests for help after the flood crisis hit the state.

There have been 133 flood-related rescues.