CARLSBAD, California (REUTERS) - Firefighters deployed air tankers, bulldozers and hand crews to battle a fast-moving wildfire just west of Yosemite National Park on Sunday (July 24) that suddenly grew into one of the largest fires of the year, forcing thousands of evacuations.

Fuelled by extreme heat and tinder-dry forests and underbrush, the Oak Fire that began on Friday closed within 0.8km from the town of Mariposa Pines, population 1,400, but was still more than 16km from Yosemite, famed for its giant, ancient sequoia trees.

As of Sunday morning, the fire had consumed 5,780 hectares, more than half the size of Paris, and was zero per cent contained, according to the California Department of Forestry and Fire Protection (Cal Fire).

More than 3,000 people are under mandatory evacuation orders and another 2,000 are under a fire advisory, meaning they could soon be ordered to leave, a Cal Fire spokesperson said.

Firefighters had the most success establishing fire retention lines on the western side of the fire, but the fire also encroached further east towards the town of Mariposa Pines and in the direction of Yosemite, said Justin Macomb, a Cal Fire operations section chief, in a midday briefing.

"The fire is roughly about a half a mile away from Mariposa Pines at this time, but we have a good plan for today to protect the community of Mariposa Pines," Macomb said.

The cause of the fire remains under investigation.

Yosemite, about an hour's drive from Mariposa County, is home to some of the largest and oldest sequoia trees in the world. The trees had been threatened by another wildfire earlier this month, but firefighters managed to save them.

More than two decades of drought and rising temperatures have conspired to make California more vulnerable than ever to wildfires, with the two most devastating years on record coming in 2020 and 2021, when more than 2.75 million hectares burnt, an area greater than the size of Rwanda.