Indonesian officials -- who have been under fire for failing to warn people ahead of last week's deadly tsunami on Java island -- recorded the quake at 6.6 and said it had the potential to trigger destructive waves.
They later said no tsunami was generated and told residents to return home.
The magnitude 6.1 quake struck 67 miles south of Gorontalo in northern Sulawesi, according to the U.S. Geological Survey. It was felt across parts of Sulawesi, but there were no reports of damage or injuries.
Fauzi, an official at Indonesia's geological agency, said officials there gave the quake an initial strength of 6.6. Different agencies often give different magnitudes for quakes and revise the figure later after analyzing more seismographical data.
Like many Indonesians, Fauzi uses a single name.
Sgt. Daule, a police officer in the coastal town of Luwuk, said hundreds of people there fled to higher ground after the quake struck, shouting "Beware tsunami! Beware tsunami!"
Just over 1 1/2 hours later, Fauzi said that no tsunami had occurred.
"We are sending a message to the people to go home because the situation is now safe," he said.
Sulawesi is 1,200 miles northeast of the capital, Jakarta.
Last Monday's tsunami was triggered by a 7.7 magnitude quake off Java's southern coast. It pummeled a nearly 200-mile stretch of coastline, killing at least 668 people.
Indonesia is on Pacific "Ring of Fire," an arc of volcanoes and fault lines encircling the Pacific Basin, and is rocked by earthquakes on a near daily basis.