New Delhi, April 20 -- A powerful undersea earthquake off Japan's northeastern coast has triggered tsunami warnings across three prefectures, as a series of significant tremors continues to rattle the Pacific region.

The ground shook across northern Japan on Monday afternoon when a 7.5-magnitude earthquake struck in Pacific waters off the coast of Iwate prefecture, sending tremors strong enough to reach Tokyo, hundreds of kilometres to the south. The Japan Meteorological Agency issued an immediate tsunami warning, cautioning residents in Iwate, Aomori and Hokkaido prefectures to brace for waves of up to three metres.

The major quake struck Northern Japan at 4:53 pm local time, with its epicentre located in the Pacific Ocean at a depth o...