A powerful earthquake has hit the north east coast of Japan and a tsunami alert has been issued for the region. 

The US Geological Survey (USGS) says it measured 7.8 on the Richter scale.

It was felt in Tokyo and reports from the capital suggest buildings have been swaying violently.

A 1 metre high tsunami wave has reportedly hit the Ishinomaki region following the tremor.

A US early warning agency reported that powerful quake had struck off the north-eastern coast but did not generate a Pacific-wide tsunami.

There was no threat of a tsunami in the wider Pacific Ocean according to the US-based Pacific Tsunami Warning Centre.

But it warned an earthquake of that magnitude could generate a tsunami that can be destructive for local coastlines.

Residents urged to 'just run'

Tokyo Electric Power says workers at the Fukushima nuclear plants are safe inside the facility despite earlier reports of an evacuation.

The plant was badly damaged in a separate earthquake and tsunami back in March 2011.

It is the largest nuclear disaster since the Chernobyl disaster of 1986.

Journalist Najib El-Khash is in Tokyo.

He says officials are making urgent appeals to people living in the north of the country.