Australian firefighters are working desperately to try to contain a series of massive wildfires burning in mountains west of Sydney.

Air pollution in parts of Sydney spiked to dangerously high levels as smoke and ash blanketed the city and high temperatures and winds are forecast.

More than 200 homes have been destroyed in New South Wales since last Thursday, after fires tore through farm and bush land and scattered communities on Sydney's outskirts.

The insurance council of Australia said claims of more than A$93 million (€65m) were expected to increase and the NSW government has declared a state of emergency.

One man died of a suspected heart attack last week while trying to defend his home from a fire north of Sydney.

Around 60 fires are still burning, with the largest and most dangerous in the Blue Mountains around 100km west of Sydney, New South Wales Rural Fire Service Commissioner Shane Fitzsimmons said.

Thousands of firefighters, hundreds of fire engines and 90 aircraft are battling the blazes, which have burned through more than 300,000 acres and have a perimeter of 1,600km, he said.

With steep terrain carpeted by tinder dry eucalyptus forests and dotted with small communities, the Blue Mountains are a popular day trip from Sydney.

However, its rugged and often inaccessible terrain can become a fire nightmare during the long, hot Southern Hemisphere summer.

"You are talking about some of the most beautiful, scenic country in the world but it is an awful challenge for firefighting and fire management," Mr Fitzsimmons said.

Efforts had been concentrating on back-burning vegetation to reduce the fuel available for the fires, bulldozing containment lines, and merging two large fires into a single blaze that would be easier to control.

A storm cell is moving towards the region, while strong, dry westerly winds gusting to 80km/h and temperatures in the mid-30 degree Celsius range are predicted.

Police arrested two boys suspected of starting fires in the Hunter Valley north of Sydney.

With dry weather and a massive land area, Australia is particularly prone to brushfires.

In 2009, the "Black Saturday" wildfires in Victoria state killed 173 people and caused $4.4bn worth of damage.

New South Wales has just experienced the warmest September and warmest 12 months on record, according to the Bureau of Meteorology.