At least 14 people have died in floods and landslides caused by days of torrential rain in South Korea, the country's disaster management office has said.

There are fears the death toll could rise as emergency rescue efforts continue, with 12 people reported missing.

Footage showed people wading through thick mud in the landslide-hit resort town of Gapyeong on Sunday as they made their way across a damaged bridge to evacuation shelters.

Further south, an entire village was covered with earth and debris following a landslide in the central Chungcheong region, according to video footage from Saturday.

Much of the destruction has been in the country's south, with six people killed and seven missing in Sancheong.

Thousands of roads and buildings have been damaged and submerged by raging floodwaters, with reports of damage to farmland and the widespread death of livestock.

Across the region, nearly 10,000 people have evacuated their homes since the downpour began on Wednesday, while more than 41,000 households have temporarily lost power, local media reported.

The rain has largely subsided in the worst-hit southern and central areas, but overnight the downpours moved north, and more heavy rain is still expected in the capital Seoul and northern regions on Sunday.

President Lee Jae-myung ordered the worst-hit areas to be declared as special disaster zones on Sunday and the government has launched a multi-agency recovery effort.

Interior minister Yun Ho-jung asked local authorities to mobilise "all available resources" swiftly.

A landslide in the northern Gapyeong County killed two people when several properties were engulfed in mud, AFP reported, citing government officials.

The rainfall is expected to end late on Sunday, but will be followed by an intense heatwave.