The US Geological Survey said that the quake occurred at a depth of 18.5km under the sea and was located 112km north of the second-largest island town in East Nusa Tenggara province.
The casualties from the undersea earthquake are not immediately clear. However, authorities said several buildings and public properties suffered damage as photos showed roads cracked open by the temblor.
Another photo by local media showed a wall demolished due to the impact of the quake and bricks strewn on the road in South Sulawesi.
Almost two hours after the quake, Indonesia’s Meteorology, Climatology, and Geophysical Agency agency called off the tsunami warning but asked locals in East Nusa Tenggara and South Sulawesi to remain vigilant.
Hazardous tsunami waves are possible for coasts located within 1,000km of the epicentre, the US-based Pacific Tsunami Warning Centre had said in the initial warning.
Preliminary visuals from the island nation showed people rushing out of their homes, away from the sea and running towards safe areas.
“Everyone ran out into the street,” according to a resident of Maumere town on Flores island.
Areas facing immediate threat of tsunami include Maluku, East Nusa Tenggara, West Nusa Tenggara and Southeast and South Sulawesi.
Aftershocks of 5.6 magnitude from the quake were felt in Larantuka, authorities said. The quake was also felt strongly in Makassar in South Sulawesi, according to reports.
The quake was felt for several minutes, forcing more people to rush out of their homes, said Alfons Hada Betan, head of the East Flores Disaster Mitigation agency.
People in coastal areas were urged to get away from the beach lines, especially from the northern side, “as there was a big tsunami there back in 1972”, said chief of Flores Timur district Anton Hayon.
Prone to strong earthquakes, Indonesia last suffered a major earthquake of 6.2 magnitude in January which claimed 105 lives and injured close to 6,500 in West Sulawesi province.
The undersea quake comes exactly 10 days after the Mount Semeru volcanic eruption in the island nation in which at least 48 people were killed and hundreds were injured.
Placed around the “Pacific Ring of Fire”, Indonesia rests on an area of high seismic activity and has already seen four earthquakes this year over the magnitude of 5.0.