At least 16 people have been killed on Sumatra when flash floods and a landslide struck the Indonesian island.

The military and rescue officials have been deployed to four affected areas. Six people are still missing, officials said on Monday.

Mud, rocks and trees tumbled down a mountain after torrential rains over the weekend, and rivers burst their banks, tearing through four hilly districts in North Sumatra province, washing away houses and destroying farms.

Police, soldiers and rescue workers used excavators, farm equipment and their bare hands to sift through the rubble, looking for the dead and missing in Semangat Gunung, a resort area in Karo district, said Juspri M Nadeak, who heads the local disaster management agency.

Rescuers recovered six bodies after a landslide hit two houses and a cottage late on Sunday, he said. Nine injured people managed to escape, he said. Rescuers on Monday were still searching for four missing people, including two children.

Rescuers on Sunday pulled two bodies from a river after flash floods swept away at least 10 houses and damaged about 150 houses and other buildings in villages in South Tapanuli district, said Puput Mashuri, who heads the local disaster management agency.

Flash floods on Sunday killed four people in Deli Serdang district, and rescue workers on Monday were searching for two people who were swept away by flash floods and are still missing.

A landslide hit several houses in Harang Julu, a mountainside village in Padang Lawas district, said Mustari, the chief of the local search and rescue agency, who like many Indonesians goes by a single name.

Rescuers late on Saturday pulled out the bodies of a four-member family, including two children, and rescued at least three injured people from the devastated village, he said.

Dozens of people were injured by the flash floods, which swept over more than 130 hectares (321 acres) of farmland and plantations.