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

The quake hit at 2.05am (1805 GMT Monday, 2.05am Singapore time), causing buildings to sway in most of the island, the Taiwanese Seismology Centre said.

It put the quake's epicentre at 57km east of Hsiulin, a town in the east of Taiwan, with a depth of 9.4km under the sea.

It issued no immediate tsunami alert.

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

A second tremor struck at 4.28am with a magnitude of 5.1 at a depth of 35km 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. -- AFP