Also, a tsunami warning has been issued after this quake struck off the east coast of Sulawesi Island, Indonesia.
"We have issued a tsunami warning as this quake is potential for that", the official in charge of the agency told Xinhua over phone.
Video footage from Luwuk city showed scared residents - some carrying children - running from their homes and racing to higher ground on motorcycles.
It had estimated the wave at under a half a metre (20 inches). However, the tremors were felt there and caused people to run into the streets in panic.
Aftershocks rippled across the east coast of Sulawesi - an island where thousands were killed in a quake-tsunami previous year - as officials scrambled to assess whether there are any casualties or major damage. Hence, resulted the residents to flee to higher ground.
Last September, a 7.5-magnitude quake and a subsequent tsunami in Palu on Sulawesi island killed more than 2,200 with a thousand more declared missing.
The force of last year's quake saw entire neighbourhoods levelled by liquefaction - a process where the ground starts behaving like a liquid and swallows up the earth like quicksand.
The BMKG, after carrying out further analyses, changed the scale of the major natural disaster which rattled C. Sulawesi on 18:40 WIB from 6.9 magnitude to 6.8 magnitude.
"There's a little bit of damage, but nothing significant and there are no casualties", he said.
As Indonesia lies in the highly seismic Ring of Fire, an area in the basin of the Pacific Ocean.
Past year was also particularly tough, when Indonesia experienced more than 2,500 disasters ranging from a series of deadly earthquakes to killer landslides and volcanic eruptions.