A powerful earthquake with preliminary 7.5 magnitude rocked the entire island of Taiwan early Wednesday, collapsing buildings in a southern city and creating a tsunami that washed ashore on southern Japanese islands.

The Japan Meteorological Agency (JMA) forecast a tsunami of up to three metres for the southern Japanese island group of the Okinawa prefecture.

A wave of 30 centimetres was detected on the coast of Yonaguni island, approximately 111 kilometres off Taiwan's east coast, about 15 minutes after the quake struck.

JMA said waves likely also hit the coasts of Miyako and Yaeyama islands.

Taiwan's earthquake monitoring agency gave the magnitude as 7.2, while the U.S. Geological Survey put it at 7.5.

The quake struck at 7:58 a.m. on the other side of the island from the capital, but was strong enough to knock items off shelves in the city.

Television showed buildings in the eastern city of Hualien shaken off their foundations.

Island-wide train service was suspended, as was subway service in Taipei.

More to come.