The US state of California is struggling to contain huge wildfires burning forests and homes warned Governor Gavin Newsom on Friday as more than 12,000 firefighters battle the blazes that have killed six people, BBC News reported.

Help is on its way from several US states as Governor Newsom put in a plea for assistance from Australia and Canada.

Among the 560 fires are some of the largest the state has seen.

More than 12,000 dry lightning strikes started the blazes during an historic heat wave in which thermometers in Death Valley National Park reached what could be the highest ever temperature reliably recorded.

By Friday, emergency officials said some of the fires had doubled in size from the day earlier and have now forced 175,000 residents to flee.