Twenty-nine people were killed and 26 injured in a major blaze at a building housing a sports centre and public bath in the central South Korean city of Jecheon, the fire agency said on Thursday.
"All victims were found at a public sauna in the building," a spokesman for the National Fire Agency said.
The fire station said 12 women and three men were known to have been killed. Thirteen bodies were unrecognisable.
Television footage showed an eight-storey building consumed by flames issuing dark plumes of smoke, as several people stood waiting for help on the outdoor terrace.
The fire, believed to have started at a parking lot on the first floor, has been mostly put out, but the death toll may rise further as firefighters continue to search the building, the spokesman said.
“The fire produced so much toxic smoke so quickly, leaving many people unable to evacuate,” the spokesman said.
Jecheon is in central South Korea, about 120 kilometres (75 miles) southeast of the capital Seoul.
President Moon Jae-In expressed regret over the accident and urged officials “utmost efforts” for rescue and search operations, his office said.
The worst fire accident ever to hit the modern South Korea was an arson attack on a subway station in the southeastern city of Daegu that killed 192 people in 2003.
