SEOUL, July 16 (AFP) - Rescuers battled to reach people trapped in a flooded tunnel Sunday in South Korea, where at least 33 people have died and 10 are missing after heavy rains caused flooding and landslides.

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 33 people had been killed and another 10 were missing in the heavy downpours, mostly buried by landslides or after falling into a flooded reservoir.

Rescue workers were still struggling to reach more than 10 cars trapped in a 430-metre (1,410-foot) underground tunnel in Cheongju, North Chungcheong province, the ministry said.

The tunnel was inundated on Saturday morning after floodwaters swept in too quickly for the people inside to escape, according to the Yonhap news agency.

As of Sunday, seven 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 Yonhap.

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

Images broadcast on local television showed a torrential stream of water from a nearby river that had burst its banks flooding into the tunnel, as rescue workers struggled to use boats to get to people inside.