At least three firefighters and a public servant have been killed in a wildfire in South Korea, prompting the government to declare a state of emergency in southeastern regions, authorities said on Saturday.

The fire, which began in Sancheong County on Friday afternoon, prompted the deployment of 304 personnel, along with 20 helicopters, according to South Korea's Interior Ministry.

More than 200 residents in 15 southern villages have been told to evacuate, it added.

"Four people – three firefighters and one public servant – have been confirmed to be dead," said a fire agency official.

Wildfires occurred in several other areas across the country, with 16 instances reported on Saturday alone, according to the Korea Forest Service.

The Interior Ministry later declared a state of emergency in Ulsan and North and South Gyeongsang provinces, due to "the extensive damage caused by simultaneous wildfires across the country."

The forest agency has issued "severe" fire warnings, its highest level, in 12 locations, including North and South Gyeongsang provinces, Busan and Daejeon.

Sancheong, in South Gyeongsang province, is about 250 kilometres southeast of Seoul.

Sections of the highways in the region have been closed as a safety measure, according to local reports.

Choi Sang-mok, South Korea's acting president, told relevant agencies to "mobilise all available equipment and personnel to quickly extinguish" the fire, his office said. (AFP)