SEOUL, South Korea—Thousands of South Korean firefighters and troops were battling a large wildfire on Saturday that tore through an eastern coastal area and temporarily threatened a nuclear power station and a liquified natural gas plant. The fire, which began Friday morning on a mountain in the seaside town of Uljin and has spread across more than 6,000 hectares (14,800 acres) to the nearby city of Samcheok, destroyed at least 159 homes and 46 other buildings and prompted the evacuation of more than 6,200 people. Images from Uljin and Samcheok showed large swaths of white and gray smoke emerging from the slopes of mountains that cover the country’s eastern coast and firefighters operating water hoses amid thick, smoky air. There were no immediate reports of injuries or deaths. Officials were investigating the cause of the blaze, which grew rapidly amid strong winds and dry conditions, South Korea’s Ministry of the …