Taiwan's strongest earthquake in 25 years has killed at least four people, with dozens more injured.

Video shows buildings half collapsed in the county of Hualien, near the quake's epicentre.

Taiwan correspondent William Yang says while the casualties appear to largely be in that area, the disruption has been more widespread.

"In the capital city here in Taipei, all metro lines have been suspended for more than an hour, and also the high-speed rail that runs along the west coast of Taiwan was also suspended."

The quake triggered tsunami alerts for southern Japan and the Philippines, which were later downgraded.

There's 137 New Zealanders registered in Taiwan, and 428 in Japan.

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