The number of fatalities was unclear, but Japan's Kyodo news reported at least 10 killed and numerous injured.
The quake prompted at least 19 countries and numerous Pacific islands to issue tsunami warnings. It was followed by powerful aftershocks that were felt in capital of Tokyo.
The quake's epicenter was 373 kilometers (231 miles) away from Tokyo, the United States Geological Survey said. But residents there continued to feel aftershocks long after the quake