The quake struck at 5:07 am (2107 GMT Friday), with the epicenter located 25.6 kilometers (16 miles) off the island's southeastern coast, at a depth of some 51 kilometers, seismologists said.
Taiwan, which lies near the junction of two tectonic plates, is regularly hit by earthquakes. The worst, measuring 7.6 on the Richter scale, rocked the island in September 1999 and left some 2,400 people dead.