Wildfires have forced nearly 3,000 people from their homes in southeastern Australia, menacing the suburbs of Sydney and blanketing the capital in haze Wednesday.

The number of fires jumped to 100 from about 70 on Christmas Day, fanned by winds of 35 miles per hour. Fire officials say many were caused by lightning but suspect seven were deliberately lit.

The fires have destroyed homes, isolated towns and cut highways and rail links across New South Wales state and around Sydney. Ambulance crews have treated hundreds of firefighters and residents for problems with respiration.

About 5,000 firefighters are battling the flames, many of them for the fifth straight day.

The first blazes started in rural areas amid sweltering summer temperatures. Winds gusting up to 55 mph and 95-degree temperatures on Christmas Day left fire crews helpless to contain the flames.

"We have never seen anything like that before," said the state fire chief, Phil Koperberg.

Thousands of properties have been threatened and 140 destroyed.

A grimy yellow haze hung over Sydney, the result of fires running north to south along its western perimeter, some less than 15 miles away. Sandra Rogers said her home in one western suburb had survived but now stood in a blackened wasteland.

"Everything has burnt around us, there's nothing left to burn," she said. "It's just absolutely devastating."

On the city's southern fringe, the world's second oldest national park was being razed by a fire burning north along a six-mile front. Two villages on the northern edge of the Royal National Park were under threat while two others had been evacuated.

Thousands of residents were being told to hose down and fireproof their homes, stay indoors and await possible evacuation.

About 12,000 homes remained without power and some without water.