The quake hit Talaud Islands, a small archipelago off Sulawesi near the Philippines, and of the 37 people injured there, nine were in serious condition, said Rustam Pakaya, head of the Health Ministry's crisis centre.
At least 31 houses, a hospital and three health clinics were damaged but there were no reports of fatalities, he said.
Series of quakes rock eastern Indonesia, three killed
The quake, at a depth of 35 km, occurred at 1734 GMT on Wednesday, the US Geological Survey said.
The Detik.com news website said residents in the town of Melonguane fled to higher ground in panic, fearing a tsunami.
The Meteorology and Geophysics Agency, which put the magnitude of the first quake at 7.4 on the Richter scale, has lifted an initial tsunami warning, said an official at the agency, Sutiono.
Sixty-two aftershocks measuring as high as 5.7 on the Richter scale were recorded since the biggest quake, said Sutiono, who, like many Indonesians goes by only one name.
He had earlier said several houses and government buildings collapsed.
Indonesia sits in the so-called Pacific Ring of Fire, a chain of fault lines and volcanoes noted for seismic activity.
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