Authorities in South Korea are battling wildfires that have doubled in size in a day in the country’s worst ever natural fire disaster.

At least 27 people have died and hundreds of buildings destroyed in the south-eastern province of North Gyeongsang, with the country’s disaster chief saying the fires had exposed the “harsh reality” of global heating.

Pointing to ultra-dry conditions and strong winds that have worsened the damage, Lee Han-kyung, disaster and safety division chief, said: “This wildfire has once again exposed the harsh reality of a climate crisis unlike anything we’ve experienced before.”

The affected areas have seen only half the average rainfall this season, while the country has experienced more than double the number of fires this year than last.

More than 36,000 hectares (88,960 acres) have been charred or were still burning in the largest of the fires, which began in the central Uiseong county, making it the biggest single forest fire in South Korea’s history. About 37,000 people have been displaced, the Yonhap news agency said.

“We are nationally in a critical situation with numerous casualties because of the unprecedented rapid spread of forest fires,” the acting president, Han Duck-soo, told a government response meeting, adding that the high number of older victims, including those in nursing hospitals, was a particular concern.

The military has released stocks of aviation fuel to help keep firefighting helicopters flying to douse flames across mountainous regions in the province, where fires have been burning now for nearly a week. More than 300 structures had been destroyed, officials said.

As of Thursday morning, authorities were mobilising more than 9,000 people and about 120 helicopters to battle the fires, the government’s disaster response centre said.

The country’s disaster chief said the wildfires were now “the largest on record”, having burned more forest than any previous blazes. The last major wildfire, in April 2020, scorched 23,913 hectares across the east coast.

“The wildfire is spreading rapidly,” Lee said. “The forest damage has reached 35,810 hectares, already exceeding the area affected by the 2000 east coast wildfire, previously the largest on record, by more than 10,000 hectares.”

The fatalities include a pilot whose helicopter crashed during efforts to contain a fire and four firefighters and other workers who died after being trapped by fast-moving flames driven by strong winds.

A satellite image showing smoke from fires burning in South Korea’s Uiseong county. Photograph: Nasa Worldview/Reuters

Authorities have not disclosed details of the civilian dead, except that they are mainly in their 60s and 70s. They suspect human error caused several of the wildfires that began last Friday, including cases where people started fires while clearing overgrown grass from family tombs or with sparks during welding work.

Last year was South Korea’s hottest year on record, with the Korea Meteorological Administration saying that the average annual temperature was 14.5C – two degrees higher than the preceding 30-year average of 12.5C.

Yeh Sang-Wook, professor of climatology at Hanyang University in Seoul, said the lack of rainfall had dried out the land “creating favourable conditions for wildfires”.

“This can be seen as one of the fundamental causes,” he said. “We can’t say that it’s only due to climate change, but climate change is directly [and] indirectly affecting the changes we are experiencing now. This is a simple fact.”

The blazes were threatening two Unesco world heritage sites – Hahoe Village and the Byeongsan Confucian academy – in Andong city on Wednesday, a city official said, as authorities sprayed fire retardants to try to protect them.

Andong and the neighbouring counties of Uiseong and Sancheong, as well as the city of Ulsan, have been hardest hit. On Wednesday night, strong winds and smoke-filled skies forced authorities in Andong, in the south-east, to order evacuations in two villages, including Puncheon, home to the Hahoe folk village, founded around the 14^th-15^th century. Hikers were advised to leave the scenic Jiri mountain as another fire spread closer.

The wildfires originated in Uiseong and have been moving rapidly eastward, spreading almost to the coast, carried by gusty winds and with dry conditions aggravating the situation.

The meteorological agency has forecast some rain for the south-west but precipitation is expected to be under 5mm for most of the affected areas.

“The amount of rain is going to be small so it doesn’t look like it’ll be big help in trying to extinguish the fire,” said the Korea Forest Service minister, Lim Sang-seop.

Officials said earlier this week that firefighters had extinguished most of the flames from the largest wildfires in key areas, but wind and dry conditions allowed them to spread again.

Houses, factories, vehicles and some historic structures have been destroyed in the fires. In Uiseong, about 20 of the 30 structures at the Gounsa temple complex – which was said to be originally built in the 7^th century – have been burned. Among them were two state-designated “treasures” – a pavilion-shaped building erected overlooking a stream in 1668, and a Joseon dynasty structure built in 1904 to mark the longevity of a king.

A monk looks at a cracked temple bell remaining after a wildfire destroyed most of the buildings at the Gounsa temple in Uiseong, South Korea. Photograph: Yasuyoshi Chiba/AFP/Getty Images

Experts have said the Uiseong fire showed extremely unusual spread in terms of its scale and speed, and that climate change was expected to make wildfires more frequent and deadly globally.

Higher temperatures amplified by human-caused climate change contributed to the existing seasonally dry conditions, “turning dry landscapes into dangerous fire fuel” in the region, said the Climate Central group, an independent body made up of scientists and researchers.

Justin McCurry and agencies

With Reuters, Associated Press and Agence France-Presse