Landslides and floods are frequent in Indonesia, where tropical downpours can quickly soak hillsides and years of deforestation often mean there is little vegetation to hold the soil.
Chalid Muhammad, director of Indonesia's leading environmental group Walhi, said the government had not done enough to prevent the disasters.
"For five consecutive years landslides and floods have occurred in Java, claiming many lives. The main trigger is ecological destruction caused by deforestation, forest conversions and chaotic spatial planning," Chalid told Reuters.
He said deforestation on Java island had reached a critical stage.
"There have been no adequate efforts by the government to protect the people from disasters. When the landslides happened officials were on holiday and there was no access of heavy equipment to the affected areas," he said.
An official said on Wednesday the main area affected by the landslides was heavily forested.
Thousands of villagers who lost their homes to floods or landslides have moved into temporary shelters in offices and schools and into tents set up by the rescue teams.