Four killed by wildfires as heat wave heads east

Four people have died in one of a series of wildfires sparked by lightening in WesternAustralia, police said on Wednesday, a deadly start to the country's summer bushfire season.

Western Australia police said the deaths occurred in the North Cascade fire near Esperance, in the state's southwest, where some 300,000 hectares have been burned. The blaze is one of three major fires burning in the state since Sunday.

"There was an inland trough that brought hot, dry and windy conditions, creating these catastrophic fire conditions," said Darryl Vink, forecaster at the Bureau of Meteorology (BOM).

The imminent bush risk for the affected Western Australia region has eased in recent hours, Vink said, but as the weather system moves east, it will increase the risk for South Australia.

The areas of South Australia at biggest risk of bush fires are rural regions, but forecasters said much of the state remains in "severe fire danger" with high temperatures, strong winds and low humidity likely to continue into Thursday.

Temperatures in South Australia are set to ease slightly on Thursday, data from the BOM shows, but will remain at nearly 35 degree Celsius (95 degrees Fahrenheit).

Soaring temperatures are also expected across Australia's east coast, forecast to top nearly 40 degrees in Sydney - the country's largest city, unusual for so early in the summer.

Wildfires are an annual event in Australia, but signs of rising summer temperatures have prompted some scientists to warn that climate change could increase the length and intensity of the fire season.

The hot, dry, windy conditions have spurred comparisons to the "Black Saturday" fires of 2009 which killed almost 200 people in the state of Victoria.