People watch their collapsed houses after a landslide caused by heavy rain in Yecheon, South Korea. Image Credit: AP

Thirteen bodies were recovered from a tunnel in South Korea as the flooding death toll across the country rose to at least 40.

Cars were trapped in a tunnel underpass in Osong near the city of Cheongju, about 70 miles south of Seoul, when the Miho River burst its banks on Saturday.

More than 10 vehicles including a bus were flooded and 13 people were killed, with nine rescued at the scene, the Ministry of Public Administration and Safety said in a statement on Monday.

The search operation is ongoing through continuing heavy rain, it said.

Up to 23 inches of rain has fallen on South Korea since Thursday, triggering landslides and road collapses, wiping out crops, and damaging homes and other buildings.

There have been 40 deaths across the country, and nine people remain missing, one in the southern port city of Busan and eight in the southeastern North Gyeongsang province, the ministry said.

Heavy rain is expected in the country's south on Monday, with rainfall totals of 2.5 inches per hour possible on Tuesday, the Korea Meteorological Administration said in a news release. Jeju Island, off the south coast, could receive up to 3.1 inches per hour on Wednesday, it warned.

President Yoon Suk Yeol on Monday returned to the country after a trip to Ukraine and other European nations. During a news conference, he said unusual weather events had become "our new normal."

"We need to completely dismantle thinking that these extremes are an aberration," he added.

In a news release issued by his office on Sunday, he also appeared to chastise local governments for their lack of preparedness, including in failing to block off entry into low-lying areas ahead of and during the floods.

South Korea has an annual monsoon season, but this was its second consecutive year of significant flooding. Last August, at least 11 people died, including some of Seoul's most vulnerable residents who live in semi-underground apartments.

South Korea, Japan, India and the Northeastern United States have all experienced serious and deadly flooding recently. Five died overnight Saturday in Pennsylvania, which followed deluges in Vermont and New York state, and at least three people died in Japan and 100 in northern India this month.