(Image source from: Yahoo)

A ferocious wildfire rushing across Northern California has destroyed parts of the Sierra foothills, including one town, officials say.

The alleged Camp Fire, which began early on Thursday near Camp Creek, has been fueled by strong winds and dry forest.

The state fire officials said some residents in the town of Paradise, which was "devastated", were trapped by the flames.

Thousands in the region have evacuated, including from schools and infirmaries.

There are unofficial reports of casualties, which an official said could take days to confirm.

"[Paradise] is devastated, everything is destroyed. There's nothing left standing," said Scott Maclean, the state's forestry and fire protection spokesman.

The Camp Fire had burned through 20,000 acres as of Thursday afternoon, local time, according to California Fire officials.

As winds approached 50mph (80km/h), triggering the fire to grow speedily in just a few hours, some residents were enforced to leave vehicles and flee on foot, local media reported.

Further south in Ventura County near Los Angeles, strong winds are preventing efforts to tackle another massive blaze - a few miles from the scene of a mass shooting in Thousands Oaks that took 12 lives on Wednesday.

The second wildfire is said to have destroyed 10,000 acres, according to officials.

Evacuation orders are in place in northern California for the town of Paradise, home to about 26,000 people, as well as Concow, Magalia, Canyon, Butte Valley, and Butte Creek areas.

Emergency crews are working to rescue residents trapped there, an official said.

At least one nursing home and the Feather River Hospital were deserted and several homes were on the flame, according to the Sacramento Bee, and the region is covered with deep, pitch-dark smoke.

Thousands are in the absence of power in the region, which is just north of Sacramento.

Others described watching flames consume their property as they evacuated.

The blaze is one of 14 presently active in California. Officials have put most of Northern California is under a Red Flag Warning, which means "extreme fire behavior" can occur within 24 hours.

Many have been sharing images on social media of highways and roads flanked by fire or covered in heavy smoke and asking for aid to evacuate friends and family.

By Sowmya