The epicentre is located about 18km (11mi) south of Taiwan’s Hualien city, according to the US Geological Survey.
It is Taiwan’s strongest earthquake in 25 years, said seismology officials.
Tsunami waves of up to 3m were expected to reach large areas of Japan’s southwestern coast, said the Japan Meteorological Agency.
The Philippines’ seismology agency has also issued a tsunami warning.
Chinese state media said tremors were felt in parts of China’s south-eastern Fujian province.
“The earthquake is close to land and it’s shallow. It’s felt all over Taiwan and offshore islands… It’s the strongest in 25 years,” said Wu Chien Fu, the director of Taipei’s Seismology Centre, in a briefing to reporters.
In September 1999, a 7.6-magnitude earthquake hit Taiwan, killing 2,400 people.
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