Multiple wildfires have charred east coastal mountain areas the size of more than 30,000 soccer fields over the past five days, but firefighting efforts have made slow headway hampered by thick smoke and fickle winds, officials said Tuesday.

Firefighting authorities regard Tuesday as a watershed in their all-out efforts to contain the main fires, as the wind direction is forecast to change unfavorably in the afternoon. They initially aimed to extinguish the main fires Monday but were disturbed by thick smoke, fog and other unfavorable weather conditions.

The wildfires spurred by high winds amid dry conditions have burned an estimated 21,772 hectares of woodland, the size of 30,493 soccer fields, along the east coastal areas as of 6 a.m. Tuesday, according to the Central Disaster and Safety Countermeasure Headquarters.

In terms of damaged areas, the ongoing blaze is close to the nation's largest wildfires on record, which burned 23,794 hectares of east coast mountains in 2000.

Uljin, a North Gyeongsang county 330 kilometers southeast of Seoul, was hardest hit with 16,913 hectares burned, followed by three Gangwon Province cities -- Donghae (2,100 hectares), Gangneung (1,900 hectares) and Samcheok (772 hectares), the agency said.

As of Monday night, no casualties had been reported, but 570 facilities and homes had been damaged and 338 people in 220 households had been displaced, it added.

The fire extinguishing rates reached 50 percent in the Uljin and Samcheok areas, and 90 percent in the Gangneung and Donghae areas, the agency said, noting about 3,000 firefighting personnel and about 100 helicopters will be mobilized during the day.

"We aim to finish extinguishing the main fires in Gangneung and Donghae (on Tuesday) morning and divert some helicopters to the Uljin area," said Choi Byeong-am, head of the Korea Forest Service (KFS), in a news conference.

"We're also preparing for a long-term battle because the damaged areas are very extensive," he said.

The authorities are also concentrating their efforts on protecting the Geumgang Pine Tree colony, a massive forest of lush pine trees more than 200 years old, in Uljin.

"Sparks have flown into the Geumgang Pine Tree colony, but firefighting efforts had been under way. So far, there has been no damage to the colony," Choi said.

The blaze began Friday morning in Uljin and rapidly spread north to Samcheok in the afternoon, driven by strong winds whose speed reached nearly 30 meters per second.

Police and the KFS are speeding up their investigations into the exact cause of the wildfires in Uljin without ruling out the possibility of the fires being started by cigarette butts from motorists.

The government has designated Uljin, Samcheok, Gangneung and Donghae, ravaged by the massive wildfires, as a special disaster zone and vowed swift support for the victims. (Yonhap)