KONTAN.CO.ID - TOKYO. Japan issued a tsunami advisory Tuesday after a strong 6.4-magnitude earthquake hit the northwest of the country.

A wave of one meter (three feet) is expected to hit the coast of the Sea of Japan, north of Tokyo, the nation's meteorological agency said.

The quake registered six on the Japanese scale, which goes up to seven but there were no immediate reports of damage from the earthquake.

The US Geological Survey put the magnitude of the quake at 6.4.

Officials immediately stopped bullet train services in the region as a precautionary measure, according to public broadcaster NHK, which also said tens of thousands of households were without power.

The meteorological agency said some waves were expected to have already reached some coastlines of Yamagata and Niigata, in the northwest of the country.

The agency warned that it is "dangerous" to stay near the coast or in the sea. "Do not approach or enter the sea until the advisory is lifted," it said.

A minor change in sea levels had already been monitored on a small island off Niigata, it added. 

"All nuclear power plants have reported no abnormalities," government spokesman Yoshihide Suga told reporters.

"Strong jolts may continue."

Suga said authorities were checking for signs of damage or injuries.

Some local roads were also closed after the earthquake, which struck at around 10:22pm local time (1322 GMT).

Japan sits on the Pacific "Ring of Fire" where many of the world's earthquakes and volcanic eruptions are recorded.

A powerful quake rocked northern Japan in September and triggered massive landslides that killed 44.

Last June, a deadly tremor rocked the Osaka region, killing five people and injuring over 350.

On March 11, 2011, a devastating 9.0-magnitude quake struck under the Pacific Ocean, and the resulting tsunami caused widespread damage and claimed thousands of lives.

Editor: Herlina Kartika Dewi