Authorities are assessing damage from almost 100 bushfires burning across Australia's most populous state that have killed one man, destroyed homes and forced hundreds to evacuate.

Milder conditions in New South Wales were helping firefighters after Thursday's unseasonably hot temperatures and strong winds had compounded the conditions and threatened towns surrounding the state capital, Sydney.

Natalie Sanders, Rural Fire Service spokeswoman, said the number of fires had dropped from more than 100 overnight to 94, burning across over 500sq km.

But 28 other fires remained out of control, she said.

Rob Rogers, Rural Fire Service deputy commissioner, said cross-state firefighters were on their way to help fight the blazes, including one burning near the town of Lithgow.

Assessment teams and police were moving into the destruction zones in search of survivors and victims, he said. Officials also were trying to determine how many homes were destroyed.

"I know some information that's been passed to me that just in one street, there were 40 homes lost," Rogers told Nine Network television.

Al Jazeera's Andrew Thomas reports from Australia

The Fire Service said a 63-year-old man had a fatal heart attack while he was fighting a fire at his home at Lake Munmorah, north of Sydney, late on Thursday.

Two firefighters were admitted to hospitals with injuries, and one had undergone surgery, Barry O'Farrell, New South Wales premier, said. He did not detail the injuries.

The fire front was still visible from Winmalee on Friday, but had moved towards the neighbouring village of Springwood where homes were being evacuated.

Hundreds of residents spent Thursday night in dozens of evacuation centres in the Blue Mountains and elsewhere in New South Wales.

Most were unaware of the fate of their homes.

Rogers said firefighters would not be able to extinguish the blazes before high temperatures and strong winds are forecast to return on Sunday and Monday.

Bushfires are common throughout Australia in the warmer months.

In February 2009, the Black Saturday bushfires in Victoria state killed 173 people and destroyed more than 2,000 homes, damage amounting to $4.4bn.

Source: Al Jazeera and agencies