TAIPEI (AFP) - An undersea earthquake measuring 6.3 on the Richter scale rocked Taiwan early Tuesday, shaking people from bed, but there were no immediate reports of casualties or damage.

The quake hit at 2:05 am (1805 GMT Monday), causing buildings to sway in most of the island, the Taiwanese Seismology Centre said.

It put the quake's epicentre at 57 kilometres (34 miles) east of Hsiulin, a town in the east of Taiwan, with a depth of 9.4 kilometres under the sea.

It issued no immediate tsunami alert.

The United States Geological Survey put the quake's epicentre 137 kilometres south-southeast of the capital Taipei.

A second tremor struck at 4:28 am with a magnitude of 5.1 at a depth of 35 kilometres in a similar location, according to the USGS.

Taiwan, which lies near the junction of two tectonic plates, is regularly shaken by earthquakes. A 7.6-magnitude quake killed around 2,400 people in September 1999.

The island was hit by a series of tremors just over two weeks ago with the strongest reaching a magnitude of 5.6.