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A strong earthquake struck off northern Japan early on Saturday, causing no risk of a tsunami but leaving three people injured and shaking buildings in Tokyo, authorities said. The U.S. Geological Survey said the magnitude 6.8 earthquake hit at a depth of 47 kilometers (30 miles) off the coast of Miyagi prefecture. Two people were injured in Miyagi and another in the neighbouring prefecture of Fukushima, but none of the injuries were life-threatening, said the Fire and Disaster Management Agency.

There was no major disruption in transportation, although Shinkansen bullet trains were temporarily suspended for safety checks and some local lines were delayed, the East Japan Railway Co. said.

Miyagi prefecture, in the country's rugged northeast, was heavily damaged by the 2011 earthquake and tsunami that left more than 18,000 people dead.