There were no immediate reports of damage and no tsunami warnings were issued.
The U.S. Geological Survey says the quake was centered near Obi island at a depth of around 53 kilometers -- making it around 2,400 kilometers from the capital Jakarta.
In contrast, Indonesia's Meteorology, Geophysics and Climate Agency measured the quake at 6.4 magnitude.
Just a few weeks ago, a massive 7.7 magnitude quake rocked the northwest region of Sumatra. There were no reported deaths or injuries, but a tsunami warning was issued, causing panic for nearby Thailand and Malaysia residents.
Meanwhile last year, a quake killed more than 1,000 people on Sumatra and in 2004, around 230,000 died when a tsunami hit off Indonesia's coast.
The country sits on a series of fault lines, making it one of the most earthquake-prone in the world.
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