As of 6pm (5pm Singapore time), 4,763 people had been evacuated nationwide, according to the Ministry of Interior and Safety, as water overtopped the dam in North Chungcheong province on Saturday morning.

Local governments' evacuation orders covered more than 7,000 people at various times, according to provincial authorities.

The tally is expected to rise as more heavy rain is expected on the Korean peninsula on Sunday, the Korea Meteorological Administration forecasted.

Korea Railroad Corp said it was halting all slow trains and some bullet trains, while other bullet trains might be delayed due to slower operation, as landslides, track flooding and falling rocks threatened safety.

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A slow train derailed late on Friday when a landslide threw earth and sand over tracks in North Chungcheong province, the transport ministry said. The engineer was injured, but no passengers were on board.

In a meeting with government agencies on Saturday, Prime Minister Han Duck-soo called for the military to actively join in rescue activities, working with government officials to mobilise equipment and manpower.