Seoul, April 5 -- A forest fire burning in the mountainous region where South Korea hosted the 2018 Winter Olympics has destroyed 120 homes and caused two deaths, authorities said Friday as thousands of people fled.

The fire likely started Thursday night from a transformer spark near a resort in the town of Goseong in Gangwon province about 210 kilometers (130 miles) northeast of Seoul and then spread to the nearby mountains, according to Choi Jin-ho, a fire captain at Gangwon Fire Headquarters.

Videos posted to social media in South Korea showed tall flames shooting 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...