Heavy rains have killed about 20 people and caused thousands to evacuate their homes across the country, authorities said Saturday.
Officials said 10 people remained missing and nine others were injured.
On Friday, two people died in a building collapse triggered by a landslide in Nonsan, South Chungcheong Province.
The death toll had risen to 21 as of 4 p.m. Saturday.
Most fatalities were reported from the southeastern province of North Gyeongsang, where 16 people died largely due to landslides and housing collapses.
In other areas, one person was killed in a mudslide in the central city of Sejong, and housing collapses killed three people in the southeastern county of Yeongju and the central county of Cheongyang.
In the central city of Cheongju, a car was struck by a landslide, killing one person.
Also in the city, one person died and nine others were rescued in the morning, after an underground roadway was flooded when a nearby river overflowed.
Fire authorities said a flash flood submerged the road too quickly for drivers and passengers to evacuate.
Officials confirmed through surveillance footage that there were 19 vehicles on the flooded road but said the exact number of people in them was still unknown, suggesting there could be more victims.
The casualties are feared to rise as government agencies assess damage reported across the nation.
Some 6,400 residents in the central county of Goesan were evacuated, as the Goesan Dam began to overflow at around 6:30 a.m. Many low-lying villages near the dam were submerged, and roads and bridges connecting the villages were cut off, trapping some residents in their homes.
A total of 1,567 people from 1,002 households in 13 cities and counties had sought temporary shelters as of Saturday morning, as heavy downpours continued to fall across the country. Among them, 1,114 people could not return home due to safety concerns.
In the central city of Gongju, residents were ordered to evacuate at 9:57 a.m. as an apartment complex was flooded.
A train derailed in Cheongju at 10:58 p.m. Friday as significant rainfall triggered a mudslide. An engine driver sustained light injuries and was taken to a hospital. No other casualties were reported.
Thirty-one cases of damage to public property were reported, including 10 mudslides and six cases where roads were destroyed, while 71 cases of damage to private property were reported, including 22 flooded homes.
Electricity blackouts were reported in 13 cities and counties nationwide. While power has been restored in most places, more than 8,300 households in Mungyeong, Yeongju and Yecheon in North Gyeongsang Province still don't have electricity.
Floods swept away crops and roads. Nationwide, 97 roads remain closed, while 384 trails in 19 national parks are closed.
The Korea Railroad Corp. (KORAIL) suspended all regular trains and some KTX bullet trains that run through the country's central inland region due to heavy rains. KORAIL also warned of slower service in routes connecting Seoul to the country's southern parts, including Busan and Jeolla Province.
The Korea Meteorological Administration issued heavy rain warnings, especially for the Chuncheong and Jeolla provinces, saying heavy rains are forecast to fall across the nation until Wednesday and until next weekend for Jeju Island. The weather conditions pose a "grave" danger, it added.
Cheongyang in South Chungcheong Province has received 512 millimeters of rainfall since Thursday, and Iksan in North Jeolla Province has received 469.5 mm.
On Thursday, the Ministry of Public Administration and Security raised the natural disaster level posed by torrential rains to the highest in the three-tier system.
President Yoon Suk Yeol ordered the government to "respond to the disaster to the fullest by using all resources available."
Yoon is currently in Ukraine, where he made an unannounced visit earlier in the day at the end of a two-leg trip that earlier took him to Lithuania for a North Atlantic Treaty Organization summit and then to Poland for an official visit.
On Saturday morning, Prime Minister Han Duck-soo ordered officials to swiftly evacuate people in landslide-prone regions to minimize casualties, and do their utmost to rescue people in affected areas.
Source: Yonhap News Agency