No damage or casualties were reported from the latest strong tremor this year in an island-nation constantly bracing for a massive earthquake.

Tsunamis measuring up to 50 centimetres (20 inches) brushed the east coast of northern Japan about one hour after the undersea quake hit at 6:39 am, local officials said.

The focus of the shallow quake was about 350 kilometers (215 miles) off Japan's main Honshu island, the meteorological agency said.

Some of the highest waves were observed in Ofunato, a city in Iwate prefecture in the northern part of Honshu.

"There has not been any report of damage so far," Ofunato disaster prevention official Haruki Ito told AFP. He said some local oyster and scallop farms may have sustained damage.

Ofunato asked 3,487 households to flee their homes although only 120 residents actually followed the advice, police officials said.

The coastal village of Tanohata in Iwate also advised some 900 people to evacuate, village official Masatsugu Kikuchi said.

"It was not compulsory but hundreds of residents evacuated their homes as a precaution," he said, adding that people had later returned home.

The quake triggered an automatic suspension of the Tohoku line of the Shinkansen bullet train, but the service resumed normal operations shortly afterwards, said a spokesman for East Japan Railway.

All the tsunami warnings were cancelled two hours after the quake struck, the meteorological agency said.

Japan has one of the world's most advanced tsunami early warning and emergency response systems. Within minutes of a tremor, research centers predict whether there is a risk of a tsunami, sometimes announcing that the waves will be only centimeters (inches) high.

People living near the coast are taught to rush for higher ground if a major tsunami is detected. Several coastal towns have constructed tall ferro-concrete buildings where residents can seek shelter.

A massive undersea quake off Indonesia last December triggered a tsunami that crashed into Indian Ocean coastlines, killing more than 200,000 people.

Japan endures 20 percent of the world's major earthquakes.

Last year, 51 people were killed and hundreds injured in a 6.8-magnitude quake in the Niigata region, 200 kilometers northwest of Tokyo.

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