Tsunami alert for Japan after 7.4-magnitude earthquake - with 10ft waves expected 'immediately' and coastal regions told to evacuate

Japanese authorities have issued a tsunami warning after an earthquake was detected off the country's northeastern coast. 

Tsunami alert for Japan after 7.4-magnitude earthquake - with 10ft waves expected 'immediately' and coastal regions told to evacuate
Japanese authorities have issued a tsunami warning after an earthquake was detected off the country's northeastern coast.