At least 800 houses, school buildings, and one bridge were damaged by the quake in Gorontalo province, head of the crisis center of the ministry Rustam Pakaya said.
"Thirteen out of the 77 wounded persons suffer from serious injury and now are hospitalized," Pakaya told Xinhua.
A shallow quake struck after midnight with epicenter at 138 km northwest of Gorontalo city and at a depth of 10 km, meteorology agency said. The agency issued warning of tsunami but then lifted it.
The quake was followed by two moderate aftershocks of 6.0 and 5.7 magnitudes, the agency said.
Indonesia has just launched a faster high-tech tsunami warning system with a cost of over 130 million U.S. dollars to prevent the repetition of the tragedy in December 2004, when over 170,000 people killed in Aceh, Indonesia by the tsunami.
The catastrophe also killed those on coastal areas of Asia, from Sri Lanka and India to Thailand and the Maldives, bringing the total death toll to about 230,000.
Indonesia sits at a vulnerable zone called "the Pacific Ring of Fire" where two continental plates, stretching from the Western Hemisphere through Japan and Southeast Asia, meet, causing frequent volcanic movements.
La Aca Tampil, a retired military officer, was killed after his house's wall collapsed and hit him. And 23 others were injured in Kwandang village, Gorontalo province, Antara news agency quoted Abdul Wahab Paudi, a spokesman of the North Gorontalo district administration, as saying.
Officials in worst-hit Buol district of Central Sulawesi was quoted as saying that at least three people had died in the area and about 700 houses had collapsed.
Another 20 people had been hospitalized with injuries in Buol, they said.
Central Sulawesi governor HB Paliuju said communications with Buol had been cut in the quake and information was sketchy.
An official also said people of Tolitoli district of Central Sulawesi had reported collapse of buildings but no fatalities.
Two residents of Sumalata sub district were injured due to the temblor which occurred at 01:02 a.m. local time.
In Sumalata sub district alone, around 50 houses were slightly damaged, 40 were seriously damaged, and nine totally collapsed, said an local official.
Two junior high school buildings respectively located in Sumalata and Tolinggula sub districts were destroyed in the disaster. The temblor also damaged two elementary school buildings in Taluditi sub district, and one elementary school building as well as a number of houses in Pohuwatowere.
The earthquake's epicenter was located at 1.41 degrees northern latitude and 122.18 degrees eastern longitude at a depth of 10 km below sea level, around 138 km northwest of Gorontalo, and 48 km north of Paleleh, Buol District, which shares a border with Gorontalo Province.
Around 400 of the houses were leveled to the ground, Central Sulawesi Governor Bandjela Paliudju was quoted as saying on Monday.
The earthquake caused a power cut off in Buol District and destroyed a 400-meter-long bridge connecting Gadung and Paleleh sub districts.
A 200-meter long hanging bridge in Lipunoto sub district was also seriously damaged in the disaster.
Indonesia, the world's largest archipelago, sits on the Pacific "Ring of Fire," the edge of a tectonic plate prone to seismic upheaval.