Firefighters managed to extinguish most of a massive forest fire that ripped through South Korea's mountainous northern coast on Friday, destroying 135 homes and forcing more than 4 000 to flee the region that hosted the 2018 Winter Olympics.

One person was killed by what government officials said was possibly the country's biggest forest fire ever. Another person was fatally struck by an object blown over by the high winds fanning the flames.

The Ministry of the Interior and Safety said fires in in the county of Goseong and nearby coastal city of Sokcho were fully extinguished. Strong winds also carried the blaze to the towns of Gangneung and Inje, but the ministry said fires in those areas were 70 to 80% extinguished.

The fire likely started on Thursday night from a transformer spark near a resort in Goseong and then spread to the mountains, according to Choi Jin-ho, a fire captain at Gangwon Fire Headquarters. Gangwon province governs the Olympic host city of Pyeongchang and is about 210km northeast of Seoul.

Videos posted to social media in South Korea showed tall flames rising from large areas of forest, the air filled with embers and debris as cars drove by the raging fire. News photos showed a burnt-out bus, fire engulfing a hill, and residents evacuating apartment complexes and filing into gyms.

The region is close to the border with North Korea. South Korea's Unification Ministry said on Friday it plans to inform North Korea of details about the forest fires.

Shutdowns and blackouts

The ministry said 135 homes and more than 100 other buildings were burned. About 525 hectares of forest was estimated to have been destroyed.

About 60 helicopters, 300 vehicles and 17 700 firefighting personnel were being deployed, the ministry said. The fire also caused blackouts in Goseong, disruptions in telecommunications and internet services, a temporary shutdown of a highway, and delays in train services from Gangneung to Seoul.

Authorities said a 60-year-old man died because of the fire, and a woman in her 70s died after being hit by wide-angle mirror on a road that fell because of strong winds. Eleven people were treated for injuries. The government didn't comment on the nature of the injuries or how many were serious.

The office of South Korean President Moon Jae-in said he called for all available resources to be deployed.

The fire hasn't threatened the Olympic sports facilities, including the main venues in Pyeongchang, the alpine center in Jeongseon, and the skating centers in seaside Gangneung.