The U.S. Geological Survey said the 6.3-magnitude quake was centered 343 kilometers (212) miles northwest of Saumlaki, a coastal town in Maluku province, at a depth of 9 kilometers (5.5 miles) beneath the sea.
Indonesia's Meteorology, Earthquake and Geophysics Agency put its preliminary magnitude at 6.7 and said that the quake was unlikely to trigger a tsunami, said Suhardjono, the agency official who like many Indonesians uses a single name.
The world's largest archipelago, Indonesia is prone to earthquakes due to its location on the Pacific "Ring of Fire," an arc of volcanoes and fault lines in the Pacific Basin.
In 2004, a monster temblor off Indonesia's Aceh shores triggered a tsunami that killed 230,000 people in a dozen countries. Most of the deaths were in Aceh.