Among the casualties, there were 11 students of an Islamic school who died after being hit by collapsing buildings in Muara Saladi village of Mandailing Natal during flash floods on Friday, Sutopo told Xinhua news agency.
Scores of people were believed to be buried under the mud. The spokesperson said that the death toll might rise as assessment of the aftermath was still underway.
Meanwhile, landslides occurred in North Sumatra's Sibolga town, destroying scores of houses.
Soldiers, the police and rescuers were rushing to search and rescue the victims, but the operations were hampered by poor access, as the affected areas were remotely located near mountain with bad roads, said Sutopo.
The floods and landslides came after a series of catastrophes in Indonesia, including multiple strong quakes and an ensuing tsunami that left over 2,000 people dead in Central Sulawesi Province.
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