A six-point-eight magnitude earthquake struck off the coast of Japan's Miyagi Prefecture at around half past ten on Saturday morning.

NHK said there are no concerns of a quake-triggered tsunami.

Powerful trembles were observed in some areas in Miyagi, reportedly strong enough to make it difficult to walk properly without holding onto something for support. 

The Japanese government has set up a contact office at the prime ministerial crisis management center in Tokyo to brace for any contingencies.