Japan warns of increased risk of powerful quakes after magnitude 7.7 tremor rattles northeast coast

Japan has issued a special advisory, warning of an increased risk of magnitude 8 or stronger earthquakes. The alert covers more than 180 cities from Hokkaido to Chiba. It follows a powerful 7.7 magnitude tremor that rattled off the Sanriku coast — strong enough to be felt in Tokyo that is a few hundred kilometres away. No immediate damage or injuries were reported. Michiyo Ishida reports from Tokyo.