A state of emergency was declared in New South Wales yesterday amid warnings that bushfires which have already destroyed nearly 200 homes in the Blue Mountains, west of Sydney, will intensify in the coming days and threaten outer suburbs of Australia’s largest city.

With dangerously hot and windy weather forecast for the next three days, the Commissioner of the Rural Fire Service, Shane Fitzsimmons, said the state was facing its worst fire conditions since the 1960s. “The reality is, however, these conditions that we’re looking at are a whole new ball game and in a league of their own,” he said yesterday.

While dozens of fires are burning across the state, three large blazes in the Blue Mountains are causing most concern. If they join up to form a single mammoth fire front – which Mr Fitzsimmons said could “very easily” happen – the entire area, home to 76,000 people, could be in danger, requiring mass evacuations.

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There are also fears that flames could jump the Nepean River, at the foot of the mountains, and threaten densely populated suburbs of western Sydney, such as Penrith. After three days of milder weather, temperatures are expected to reach 38C in Penrith today, while winds of up to 60mph are forecast for Wednesday.

As residents of the worst-hit towns of Springwood and Winmalee returned to comb through the ruins of their homes, the NSW Premier, Barry O’Farrell, announced the state of emergency, which empowers the emergency services to carry out forced evacuations.

“There is potential for a significant and widespread danger to life and property across the state,” Mr O’Farrell said. “If the choice is life or property, the choice clearly should be life.”

More than 2,000 men and women are battling to contain the blazes. On Saturday night, they were joined by the Prime Minister, Tony Abbott, a volunteer firefighter, who helped with back-burning operations in the mountains. As of last night, 69 fires were still burning, 22 of them out of control. Some may take weeks to extinguish.

Around the state, the fires – which took hold amid hot, windy weather last Thursday – have already destroyed 208 homes and damaged 122. The only fatality so far was a 63-year-old man who died of a heart attack on the Central Coast, north of Sydney, last week while trying to protect his house.

Mr Fitzsimmons said communities in the Blue Mountains and around the Hawkesbury River, north-west of Sydney, faced “unparalleled” risks in the coming days, and he expected “significant relocation of people out of harm’s way”.

Some residents have said they plan to stay and defend their homes, but the state’s Assistant Police Commissioner, Alan Clarke, said police were prepared to enforce mandatory evacuation orders. “At the end of the day, we hope we have buildings standing. But if we don’t have buildings standing, we don’t want bodies in them,” he said.

The Australian military is investigating whether one of the major fires, which began on Defence department land near the town of Lithgow, was linked to an explosives training exercise that day. Police have charged two girls, aged 12 and 13, with starting a small fire in western Sydney, which was extinguished by firefighters.

While bushfires are common during the Australian summer, the timing of the current fires is highly unusual. Experts point to record spring temperatures following a warm, dry winter.