Bushfires razed at least 10 homes and threatened dozens more in south-eastern Australia yesterday as a heatwave brought temperatures of up to 47C (117F).

At least three houses were destroyed in Woy Woy, on the central coast 50 miles north of Sydney, and another 50 were evacuated. The fire service said that at least four fires were burning out of control in the area, with flames up to 20 metres high fanned by scorching winds. Seven cars were also ablaze in Woy Woy.

Thousands of firefighters tackled the blazes, supported by helicopters that dropped water on the flames. Major roads from Sydney to the central coast were closed, stranding thousands of holidaymakers who had flocked to the beaches to seek relief from the searing heat. It was the hottest New Year's Day on record in New South Wales and the second hottest January day.

In Sydney, the temperature reached 45C. An air-conditioning unit broke down at the airport and the heat caused power failures and delays in city train services, which were hit by faults in overhead wiring.

Sydney hospitals treated a stream of patients affected by the heat, particularly the elderly.

One man suffered burns to 60 per cent of his body after a fire scorched 58,068 acres of land in Junee, 180 miles south-west of Sydney.

"The fires are widespread and breaking out right across the state," said Rebel Talbert, a spokesman for the New South Wales Rural Fire Service.

The central coast fires were the worst of 44 burning across the state yesterday. In Victoria, a major fire destroyed seven homes as it swept across a 20-mile front, burning through bush and farmland and damaging dozens of properties. Two people were injured. Melbourne, the capital of Victoria, had its hottest New Year's Eve ever, with a high of 42.9C.

Authorities say a wet winter and spring followed by dry summer conditions have created an abundance of flammable material around the country, particularly in the New South Wales countryside.

Cooler conditions were expected by late yesterday evening but they could prompt fresh problems, with wind gusts of up to 50 miles per hour making fire behaviour very erratic.