The fires spread across the country's southeastern region on Tuesday, forcing thousands of residents to flee their homes and razing neighbourhoods, with authorities transferring hundreds of inmates from prisons.
As of 5am on Wednesday (local time), 12 people had died in a wildfire starting from Uiseong county, while four other deaths were linked to another fire from Sancheong county, according to the Safety Ministry.
The Yonhap News Agency reported later on Wednesday that the toll had risen to 18, citing data from the government.
The Uiseong fire, only 68% contained and exacerbated by strong winds, showed "unimaginable" scale and speed, said Lee Byung-doo, a forest disaster expert at the National Institute of Forest Science.
Acting President Han Duck-soo has vowed to deploy firefighting helicopters and ground personnel to battle the fires, fuelled by winds and dry weather.
Dry conditions were expected to persist in the wildfire-hit region on Wednesday, the Safety Ministry said.
Climate change was projected to make wildfires more frequent, Lee said, as wildfires that ravaged part of Los Angeles in January and a recent wildfire in northeast Japan are still relatively rare.
"We have to admit large-scale wildfires are going to increase and prepare more resources and manpower," he told a local television station.
The casualties included four people who were trying to escape the fire but their vehicle was overturned. Three died and one was injured, Yonhap News Agency reported.
The blazes that broke out on Saturday in Uiseong are yet to be contained, gutting ancient temples and destroying homes.
The government has designated the affected areas as special disaster zones, and said the fires had damaged more than 15,000 hectares.
