Hundreds of rescuers were digging through mud and rubble after the landslide buried scores of houses in Jemblung village in central Java late Friday, the national disaster agency said. The landslide swept down a hillside in the village, sparing only two houses.
TV footage showed bystanders watching the emergency effort while rescuers passed an orange body bag by hand through the muddy area.
"We found 12 bodies at the moment, and we are searching for 96 others," an officer at the emergency centre at the scene of the disaster told AFP, asking not to be identified.
"Conditions on the ground are pretty tough and we need heavy machines to clear the road that has been covered by the landslide," Nugroho added.
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Officials said that the ground was still unstable and most rescue work was being carried out manually. Heavy machines were trying to clear mud that had cut access to the location.
There was no phone signal in the area, making coordinating rescuing efforts difficult, they added.
The agency said that 200 rescuers and 500 volunteers had joined the search for the missing.
The national disaster agency estimates around half the country's 250 million population lives in areas prone to landslides.
The vast Indonesian archipelago is one of the most natural-disaster-prone nations on Earth, and is also frequently hit by earthquakes and volcanic eruptions.