A huge mudslide triggered by heavy rain crashed Thursday into homes near the mountainous Costa Rican capital, killing at least 20 people and leaving 12 others missing, rescue officials said.

A wave of mud and rocks rushed down the Pico Blanco hill at dawn and slammed into some 30 homes in San Antonio de Escazu, a southwestern suburb of San Jose, said the National Commission on Emergencies (CNE).

"They are now talking about 20 people dead," CNE spokesman Reinaldo Carballo, told AFP.

Rescuers scoured the area for 12 others missing among upturned cars, washing machines and twisted sheets of tin roofing material, all buried helter-skelter in mud that in places was waist-deep.

Among the bodies recovered at the disaster site, AFP saw those of two children.

"It sounded like airplanes approaching, then we were hit," said Ismael Morientes, who lost his home and car but managed to flee with his family.

Landslides affected other parts of the city but there were no victims, said Red Cross spokesman Freddy Roman.

President Laura Chinchilla urged that search and rescue efforts be left to trained professionals, amid reports civilians were digging around, slowing down crews already hampered in their work by driving rain.

"Even women and children are getting involved in the rescue effort... it's our duty to protect their lives," Chinchilla told a press conference in San Jose.

Later the search for survivors was suspended for the night, the Red Cross said, but rescuers planned to resume the effort at first light.

The president said the landslide had damaged main water supply lines and the government was setting up a truck delivery system to speed supplies to some 700,000 people across the country lacking potable water.

Chinchilla said her government was turning to "friendly countries" and international financial institutions like the InterAmerican Development Bank and World Bank for financial help to deal with the disaster.

Neighboring Nicaragua, which has been embroiled in a border dispute with Costa Rica, immediately offered to do whatever possible to help.

Schools were closed in several Costa Rican cities, including the San Jose metropolitan area, due to heavy rain over the past 48 hours. Several towns along the country's Pacific coast were flooded and isolated.

San Antonio de Escazu, located some seven kilometers (four miles) southeast of downtown San Jose, was a poor neighborhood where smarter middle-class homes had been starting to spring up.

Floods and landslides have killed some 300 people across Central America in this year's especially violent and wet rainy season, which stretches from May to November.