Lee Gon-hee of the Central Disaster and Safety Control Center in Seoul said a further three people were missing after
Typhoon Meari skirted the west coast of South Korea at the weekend.
Meari, the Korean word for "echo," was due to make landfall in North Korea early on Monday.
The North's KCNA state news agency warned residents in the coastal areas of South Hamgyong Province and Kangwon Province to be ready for "tidal waves."
Dozens of domestic flights were canceled in South Korea on Sunday and ships ordered to stay in port. Authorities said international flights were not affected.
The historic Chilgok bridge in North Gyeongsang, built to honor soldiers killed in the 1950-53 Korean War, partially collapsed at the weekend after the Nakdong River flooded.
The same typhoon left nearly 30 people dead or missing in the Philippines and Vietnam last week.