There were no immediate reports of damage or casualties.

"The quake originated deep from the sea far off Taiwan's eastern coast so its strength was greatly reduced," said the center's deputy director Lu Pei-ling.

"It was a normal release of force," Lu said, adding the submarine tremor was not expected to impact on the island.

The quake hit at 10:28 pm (1428 GMT) with an epicenter 65 kilometersmiles) east of the eastern coastal city of Suao, 84.2 miles under the seabed.

Taiwan's worst earthquake, measuring 7.6 on the Richter scale, struck in September 1999, leaving some 2,400 people dead.

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