A person has died in the city of Osan, where a ten meter high retaining wall collapsed onto the road and crushed the man's car.
Three other people have been reported dead in separate incidents, including in a river and a flooded basement, according to the Ministry of the Interior and Safety.
South Korea is usually hit by monsoon rains in July, but in three areas in the province of South Chungcheong, this week's rainfall has been among the strongest recorded since complete measurements began in 1904, the country's weather agency reports. In parts of the province, a total of 420 millimeters of rain has fallen since Wednesday.
In western Seosan, 114.9 millimeters of rain have fallen per hour. On South Korean TV, video clips are shown of extensive flooding in the area, with flooded markets and apartment buildings, and parked cars under water.
Residents of the municipality of Hongseong were urged on Thursday morning to evacuate immediately due to a flooded watercourse.
On Thursday evening, local time, nearly 1,400 people have been evacuated from their homes and 46 flights have been cancelled.
South Korea is usually well prepared for the monsoon rains and the death toll is usually relatively low. Even in 2022, record rainfall and flooding occurred, resulting in eleven deaths.
