A search and rescue operation is under way, with police and military personnel scouring rubble for the missing, National Disaster Mitigation Agency spokesman Sutopo Purwo Nugroho said.
The tragedy came after heavy rain yesterday night caused the Moa-Moa river, which cuts through the city of Ambon on the Maluku chain of islands, to overflow.
"Eight were killed and five are still missing. Another 10 were injured," Nugroho stated.
The floods submerged some houses on the river's banks and triggered landslides in several areas among Ambon's hills. Nine houses were swept away or buried and another 30 damaged.
Environmentalists blame logging and a failure to reforest denuded land for exacerbating flooding.