Rescuers battled to reach people trapped in a flooded tunnel Sunday in South Korea, where at least 35 people have died and 10 are missing after heavy rains caused flooding and landslides.

© NATIONAL FIRE AGENCYSouth Korean rescue workers search for missing people on a submerged road leading to an underground tunnel in Cheongju.

South Korea is at the peak of its summer monsoon season, and there has been heavy rainfall for the last four days, causing a major dam to overflow.

The interior ministry reported that 35 people had been killed and another 10 were missing in the heavy downpours, mostly buried by landslides or after falling into a flooded reservoir.

Seo Jeong-il, head of the west Cheongju fire station in North Chungcheong province said some 15 vehicles, including a bus, are estimated to have been submerged in the flooded, 430-meter (1,410-foot) underpass in the city shortly after a levee of a nearby river was destroyed by the downpours on Saturday.

CCTV footage aired on local broadcaster MBC showed muddy water rushing into the tunnel as vehicles drove past with their wheels submerged.

"We are focusing on the search operation as there's likely more people there," Seo told reporters. "We are doing our best to wrap it up today."

As of Sunday, eight bodies have been recovered from the tunnel and divers were working around the clock searching for more victims, the interior ministry said.

"I have no hope but I can't leave," a parent of one of those missing in the tunnel told the Yonhap news agency.

"My heart wrenches thinking how painful it must have been for my son in the cold water."

One survivor from the submerged tunnel said the government should have restricted access to the underpass when flooding was expected, Yonhap reported.

A North Chungcheong province official said the levee unexpectedly collapsed before the precipitation reached the level required for restricting access to the tunnel.

South Korean President Yoon Suk-yeol, who is currently on an overseas trip, held an emergency meeting with his aides on the government's response to the heavy rains and flooding, his office said.

Earlier, he ordered Prime Minister Han Duck-soo to mobilize all available resources to minimize casualties.

The majority of the casualties — including 17 of the dead and nine 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.

Korea Railroad Corp. has halted all slow trains and some bullet trains since Saturday due to safety concerns over landslides, track flooding and falling rocks.

More rain is forecast through Wednesday, and the Korea Meteorological Administration has warned the weather conditions pose a "grave" danger.

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.