The earthquake struck with a depth of 10.5 miles (17.5 km) and its epicenter 102km south-southwest of Luwuk, Indonesia, according to the US Geological Survey (USGS).
A spokesman for Indonesia’s Geophysical Agency said a tsunami warning has been issued.
Evacuations have begun in the region of Sulawesi, according to Sky News.
According to USGS maps, the quake would have been felt across the whole Indonesia island.
However, the USGS suggests landslides are unlikely to be triggered by the quake as “little or no area affected”.
Aftershocks of magnitudes 4.7 and 5.1 followed within minutes of the initial quake in the Gulf of Tolo.
Indonesia is situated along the seismic and earthquake hotspot know as the Ring of Fire.
More to follow.
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