Of the 77 people injured in Monday's magnitude-7.7 quake, 13 were in serious condition, said Rustam Pakaya, head of the Health Ministry's crisis centre.
Pakaya said three people were killed and 45 injured in the Buol district of Central Sulawesi province while three people died and 32 were injured by falling debris in the northern district of Gorontalo.
At least 800 buildings were damaged by the quake, he said. However, local government officials said more than 1,500 homes and buildings were damaged in Central Sulawesi province alone.
Meanwhile, the official Antara news agency reported that more than 20,000 residents remained in the hills close to their homes in the coastal Buol district for fear of possible tidal waves.
The quake's epicentre was in the sea about 138 kilometres north-west of Gorontalo on North Sulawesi, about 1,950 kilometres north-east of Jakarta. It prompted the authorities to briefly issue a tsunami warning, but the alert was canceled after no tidal waves materialized.
Indonesia, the world's largest archipelago, sits on the Pacific "Ring of Fire," where tectonic plates come together, making the region prone to seismic upheaval.
Monday's earthquake came less than a week after the country launched a high-tech system aimed at detecting potential tsunamis and providing faster alerts in a region battered by frequent earthquakes.
A major earthquake and subsequent tsunami struck in December 2004, leaving more than 170,000 people dead or missing in Indonesia's Aceh province and around 500,000 homeless. About 230,000 people were killed across the Indian Ocean. dpa sh jh ls
- Deutsche Presse Agentur
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