The quake was centred in the county of Kaohsiung, and struck at a depth of about 5 kilometres. Kaohsiung is about 400 kilometres south of the capital Taipei.
No tsunami alert was issued.
Kuo Kai-wen, director of the Central Weather Bureau's Seismology Centre, said the Taiwan quake was not geologically related to the temblor that hit Chile over the weekend, killing more than 800 people.
In the southern Taiwanese city of Tainan, a fire broke out in a textile factory shortly after today's quake struck, sending huge plumes of black smoke billowing into the air. At least one train in southern Taiwan shifted slightly off its tracks, and authorities suspended service throughout the region. Subway service in the city of Kaohsiung was temporarily disrupted.
Power outages hit Taipei and at least one county to the south, and telephone service in some parts of Taiwan was spotty. Buildings swayed in the capital when the quake struck.
The quake's epicentre was near the town of Jiashian, in the same area where a devastating typhoon struck last August. A Kaohsiung county official told CTI TV news that some temporary housing in the town collapsed as a result of the quake.
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