LOS ANGELES — At least six people have died as sky-darkening wildfires forced tens of thousands of people throughout California to flee their homes on Friday. The worst of the hundreds of fires burning across the state are in the mountains to the south and east of San Francisco. Three major complexes encompassing dozens of fires chewed through a combined 1,994 square kilometers of forests, canyons, and rural areas north, east, and south of San Francisco Bay. Thousands of acres were ablaze elsewhere in the state. Officials say the fires were started by more than 12,000 dry lightning strikes amidst a historic heatwave. Tens of thousands of homes were threatened by flames that drove through dense and bone-dry trees and brush. 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. Over 10,000 fire-fighters are battling the blazes, which have been burning on steep, difficult to access terrain and have been fuelled by strong winds. More firefighters are racing in from other states to help. Two of the fires are now the 7th and 10th largest in the state"s history, Governor Gavin Newsom said in a news conference as he urged President Trump to sign a major disaster declaration. "We simply haven"t seen anything like this in many, many years," he said, adding that an area the size of the US state of Rhode Island has already burned within California. Although temperatures were predicted to ease slightly on Friday, they were also expected to be hot enough that firefighters will not be able to count on cool evening weather aiding them. Erratic winds also could drive the fires unpredictably in multiple directions, state fire officials said. — Agencies