TOKYO: A succession of 21 earthquakes registering 4.0 magnitude or stronger struck central Japan in just over 90 minutes today, the Japan Meteorological Agency said.
The strongest jolt measured 7.6, it said. The quakes prompted tsunami warnings and authorities urged people in the area to move to higher ground.
Meanwhile, in Russia, Sakhalin island near Japan and the Pacific city of Vladivostok were on "alert" due to a possible tsunami risk after a major earthquake in Japan.
Emergency services in Sakhalin declared a "tsunami alert", saying the island's western coast "may be affected by tsunami waves."
City authorities in Vladivostok also announced an alert and ordered fishermen to "urgently get back to shore."