Officials in areas at highest risk -- the North Sulawesi capital, Manado, northern Gorontalo province and the Sangihe islands -- "are instructed to immediately direct their residents to evacuate in an orderly manner to higher ground," the national disaster agency said in a statement.

It said the jolt was felt weakly in affected areas for two to three seconds, and the situation on the ground was "safe, calm and under control" for the moment.

"The public is urged not to panic, to prioritise the safety of vulnerable groups such as the elderly, people with disabilities, and children, and to always comply with official instructions," said spokesman Abdul Muhari.

"Residents are also reminded not to spread unverified rumours or information and to always refer to regular data updates from relevant agencies and officers in the field."

Indonesia and neighbouring countries experience frequent earthquakes due to their location in the Pacific "Ring of Fire" -- an arc of intense seismic activity stretching from Japan through Southeast Asia and across the Pacific basin.

A 9.1-magnitude quake struck the westernmost Aceh province in 2004, causing a tsunami and killing more than 170,000 people in Indonesia.

The agency advised residents in areas just beyond the direct danger zone to "stay away from coastal areas and riverbanks" and to halt all activities on waterways.