Gushing streams swollen by torrential rains swept over hundreds of sleeping campers in South Korea, killing at least 20 people and leaving 70 others missing, relief officials said Saturday.

The downpours, which dumped as much as one foot of rain overnight in the southern provinces, also submerged homes and farmland, washed away roads, and triggered landslides.Most of the 70 people reported missing were swept away by the sudden rise in water levels in valleys around the Chiri Mountains, a popular hiking and camping site 135 miles south of Seoul.

In one hour, more than 5 1/2 inches of rain poured down on the mountain area, weather officials said. Weather forecasters had failed to predict the heavy rain.

"It rained so hard it looked as if somebody was pouring buckets of water over our tent. Soon the flood came and engulfed the tent," Lim June-hyun, a 13-year-old camper, told SBC-TV.

Hundreds remained stranded. Rescuers used helicopters and ropes to guide the marooned campers across raging streams to safety.

At least 100 homes remained underwater on Saturday, and 300 people were homeless, officials said. TV footage showed large stretches of rice fields underwater and cars swept away in flood water.

Gen. Kim Dong-shin, chairman of the Joint Chiefs of Staff, ordered the military to provide manpower and machinery to help relief operations.

Disaster officials said communications with the remote area was poor. They feared the casualty figures could rise.

According to news reports, a number of people were killed in nearby villages.

Kang Byung-ho, 38, and three family members were crushed to death when their home collapsed under a landslide. Villagers pulled up the body of a baby girl floating in flood water. A 29-year-old farmer was electrocuted while using an electric pump.

Two airports were closed because of the rains.