Local reports say many people remained outside through the night in fear of aftershocks.
There were no reports of significant damage or injuries due to the strong shaking.
The U.S. Geological Survey placed the undersea quake about 125 miles east of the capital, Dili, beneath the Timor Sea.
The agency said it struck at 7:09 p.m. local time at a depth of about 22 miles. Indonesia and its former territory of East Timor are prone to seismic events due to their location on the Pacific Ring of Fire.