New Delhi, April 20 -- Authorities in Japan downgraded a tsunami warning to an advisory after a powerful 7.7-magnitude earthquake struck off its northeastern coast on Monday (April 20).

The quake, which hit at 4:53 p.m. local time, initially triggered fears of tsunami waves as high as 3 metres. However, waves of up to 80 cm were recorded about two hours later, prompting officials to ease the warning level.

Japan's top government spokesperson Minoru Kihara said there were no immediate reports of casualties or major damage as of Monday evening in Tokyo.

Precautionary evacuation orders were issued in several coastal towns, including Otsuchi and Kamaishi, both of which were severely affected during the 2011 Japan earthquake and tsunami.

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