South Korea's Ministry of the Interior and Safety on Sunday said heavy rainfall had caused landslides in dozens of places and flooded residential areas and roads.
Much of the damage was in the Seoul metropolitan region and the central region of the country.
At least 5 people were reported to have been found dead while about 8 others appeared to have been swept away.
Among the dead were a woman believed to have died in a gas explosion after a landslide enveloped a cowshed, and a man who died when a chicken farm was engulfed by mud.
Three people from the same family — a woman, her daughter and son-in-law — were among those missing after torrents engulfed them in Danyang province.
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Train services were also disrupted on three train lines running in the central and eastern parts of the country. Several roads also had to be closed because of mudslides.
As of Sunday afternoon, heavy rain alerts were issued for Seoul and Gyeonggi Province, with the downpour expected to last into Monday morning. Some 360 people were reported to have been made homeless by Sunday afternoon.
rc/mm (AP, Yonhap)