SYDNEY (REUTERS) - The authorities in Australia's Queensland and New South Wales states on Monday (Nov 11) declared a state of emergency as the country's eastern region prepared for "catastrophic" fire conditions.

Fires in northern New South Wales (NSW) and Queensland over the weekend killed three people and destroyed more than 150 homes.

While Australia's most populous city Sydney avoided the worst of the weekend conditions, temperatures are set to soar to more than 34 deg C, with strong, dry winds.

The authorities raised the forecast for greater Sydney region to catastrophic fire danger for Tuesday, the first time the city has been rated at that level since new fire danger ratings were introduced in 2009.

Home to more than five million people, Sydney is ringed by large areas of bushland, much of which remains tinder dry following little rain across the country's east coast in recent months.

"Tomorrow is about protecting life, protecting property and ensuring everybody is safe as possible," NSW Premier Gladys Berejiklian told reporters in Sydney.

Lawmakers said the statewide state of emergency - giving firefighters broad powers to control government resources, force evacuations, close roads and shut down utilities - would remain in place for seven days.

On Monday afternoon, the fire service authorised use of the Standard Emergency Warning Signal, an alarm and verbal warning that will be played on radio and television stations every hour.

People in areas deemed at the greatest risk were urged to evacuate before forecast unprecedented hot and windy conditions on Tuesday, which officials fear will fan fires already burning.

NSW Rural Fire Service (RFS) Commissioner Shane Fitzsimmons urged people to evacuate before conditions worsened, warning that new fires can begin up to 20km ahead of established fires.

"Relocate while things are calm without the pressure or anxiety of fires bearing down the back door," he said.

Mr Fitzsimmons said an additional 400 firefighters on 50 trucks will arrive from the neighbouring state of Victoria to assist local authorities.

Authorities stressed that even fireproofed homes will not be able to withstand catastrophic conditions, which Fitzsimmons described as "when lives are lost, it's where people die".

More than 100 schools will be closed on Tuesday.

On Monday afternoon, rescue services were moving large animals from high risk areas, while health officials warned that air quality across NSW will worsen as winds blow smoke from the current mid-north coast bushfires south.

The fires have already had a devastating impact on Australia's wildlife, with about 350 koalas feared dead in a major habitat.

Bushfires are a common and deadly threat in Australia's hot, dry summers, a danger stoked by a sustained period of dry weather across the country's east coast.

CLIMATE CHANGE DEBATE

In February 2009, Australia's worst bushfires on record destroyed thousands of homes in Victoria, killing 173 people and injuring 414 on a day the media dubbed "Black Saturday".

The current fires, however, come weeks ahead of the Southern hemisphere summer, sharpening attention on the policies of Australia's conservative government to address climate change.

Environmental activists and opposition lawmakers have used the fires to call on Prime Minister Scott Morrison, a supporter of the coal industry, to strengthen the country's emissions targets.

Mr Morrison declined to answer questions about whether the fires were linked to climate change as he visited fire-hit areas in the north of NSW over the weekend.

Deputy Prime Minister Michael McCormack on Monday accused climate activists of politicising a tragedy.

"What we are doing is taking real and meaningful action to reduce global emissions without shutting down all our industries," Mr McCormack told Australian Broadcasting Corp radio.

"They don't need the ravings of some pure, enlightened and woke capital city greenies at this time, when they're trying to save their homes, when in fact they're going out in many cases saving other peoples' homes and leaving their own homes at risk."