Japan's most powerful earthquake since records began has struck the north-east coast, triggering a massive tsunami.

Cars, ships and buildings were swept away by a wall of water after the 8.9-magnitude quake, which struck about 400km (250 miles) north-east of Tokyo.

A state of emergency has been declared at a nuclear power plant but officials said there were no radiation leaks.

The death toll is unclear, but police say 200 to 300 bodies have been found in the port city of Sendai.

Measured at 8.9 by the US Geological Survey, the tremor struck at 1446 local time (0546 GMT) at a depth of about 24km.

Mike Wooldridge reports.