The quake struck at 1255 (0355 GMT), rocking buildings for about 30 seconds, but there were no reports of major structural damage and public transport was not seriously affected.

Seven women were injured when part of a temple wall collapsed in central Tokyo, fire brigade officials said.

The epicentre was 80 kilometres (50 miles) below the surface in the Pacific Ocean east of Tokyo, Japan's Meteorological Agency said.

Japan has rehearsed for a major quake in Tokyo

Correspondents say the emergency services in Japan are generally well prepared to cope with quakes, as the country lies at the junction of at least three tectonic plates.

Hard lessons were learnt from the Kobe earthquake in 1995, which killed more than 6,000 people and exposed serious weaknesses in emergency planning and building design.

Geologists have long predicted that a massive earthquake will hit the Tokyo area, where 30 million people live.