Seoul, July 17: South Korean President Yoon Suk-yeol on Monday (Jul 17) blamed authorities' failure to follow disaster response rules as the death toll from days of torrential grew to 40, including a dozen people found dead in a submerged underpass.

Deluges have pummelled central and southern regions since Thursday as the rainy season that started in late June reaches its peak. The interior ministry has also reported nine people missing and 34 injured across the nation.

Twelve deaths, including three bodies found overnight, occurred in a tunnel in Cheongju, 110km south of Seoul, where 16 vehicles, including a bus, were swamped by a flash flood on Saturday after a river levee collapsed.

The incident fuelled questions over South Korea's efforts to prevent and respond to flood damage. Some drivers who use the road regularly blamed the government for failing to ban access to the underpass even though floods were widely forecast.

Yoon, just back from an overseas trip, on Monday convened a disaster response meeting and conceded the situation was made worse because of poor management of vulnerable areas.

"We've repeatedly emphasised access control over dangerous areas and preemptive evacuation since last year, but if basic principles of disaster response are not kept on the spot, it is difficult to ensure public safety," Yoon told the meeting.

Nearly 900 fire, police and military officials took part in the underpass rescue operation, using boats, underwater drones and other equipment, according to the interior ministry.

Seo Jeong-il, fire chief in west Cheongju, told a briefing on Monday that while search efforts continued there were no signs of more victims in the remaining vehicles in the tunnel.

According to Yonhap, South Korean police said they would launch an investigation into the fatal flooding of the underpass in Cheongju.

Floods have claimed dozens of lives during recent rainy seasons as weather patterns have become more extreme.

The government last year vowed to take steps to better cope with climate change-induced disasters after the heaviest downpours in 115 years pounded Seoul, including the glitzy district of Gangnam, leaving at least 14 dead and flooding subways, roads and homes.

Yoon on Monday flew in a helicopter over some devastated areas. Earlier, he called for utmost efforts to rescue any remaining victims and vowed support for those affected, including designating flood-hit areas as special disaster zones.

"The government will restore everything, so don't worry too much," Yoon said after meeting residents in Yecheon in North Gyeongsang province, an area hit by landslides where 19 people died and eight remain missing.

Ahead of his visit, he said that "this kind of extreme weather event will become commonplace - we must accept climate change is happening, and deal with it".

The idea that extreme weather linked to climate change "is an anomaly and can't be helped needs to be completely overhauled", he said, calling for "extraordinary determination" to improve the country's preparedness and response.

South Korea will "mobilise all available resources" including the military and police to help with rescue efforts, he said.

"The rainy season is not over yet, and the forecast is now that there will be torrential rain again tomorrow," he added.

The majority of the casualties - including 19 of the dead and eight of the missing - were from North Gyeongsang province and were largely due to massive landslides in the mountainous area that engulfed houses with people inside.

Some of the people who have been reported missing were swept away when a river overflowed in the province, the interior ministry said.

The Korea Meteorological Administration forecast more heavy rain to Wednesday and urged the public to "refrain from going outside".

South Korea is regularly hit by flooding during the summer monsoon period, but the country is typically well-prepared and the death toll is usually relatively low.

Scientists say climate change has made weather events around the world more extreme and more frequent.

South Korea endured record-breaking rains and flooding last year, which left more than 11 people dead.

They included three people who died trapped in a Seoul basement apartment of the kind that became internationally known because of the Oscar-winning Korean film Parasite.

The government said at the time that the 2022 flooding was the heaviest rainfall since Seoul weather records began 115 years ago, blaming climate change for the extreme weather.

The situation across the border in North Korea remains unclear, but in recent weeks state media has reported on heavy rainfall and referred to measures to protect crops in a country that has suffered from serious food shortages.

At a briefing, the South's Unification Ministry said it had asked Pyongyang to notify Seoul of any plans to release water from its Hwanggang Dam. In 2009, the release of water from the dam resulted in flooding downstream that killed six South Koreans.-Agencies