The quake hit at 9:52 am (0352 GMT) and was centred 49 kilometres (30.8 miles) under the sea floor north of Talaud Islands, some 450 kilometres (279.6 miles) north-east of the North Sulawesi provincial capital, Manado.
"We have contacted Manado and they said there was no report that the earthquake had been felt in the region," said an official of the meteorology office here who identified himself as Adjat.
The Indonesian archipelago sits on the Pacific Ring of Fire, where continental plates meet, causing frequent seismic and volcanic activity.
Indonesia was the nation worst hit by the earthquake-triggered Asian tsunami in December 2004, which killed some 168,000 people in Aceh province.
A 7.7-magnitude earthquake in July on the south coast of the main island of Java also killed more than 600 people.

Copyright AFP (Agence France-Presse), 2006