A 6.3-magnitude earthquake struck northern Japan on Friday, the country's weather agency said, but no tsunami warning was issued and there were no immediate reports of damage. The quake hit at 8:22 pm (1122 GMT) in Pacific waters off northern Miyagi prefecture, according to the Japan Meteorological Agency (JMA).
It follows a powerful 7.7-magnitude earthquake that hit near the region in April, prompting a tsunami alert at the time.
The JMA has cautioned that a major quake could occur in the region, even after it lifted a special warning issued after the April tremor.
Public broadcaster NHK said on Friday that no abnormalities were detected at nuclear power plants in Miyagi and Fukushima, located about 125 kilometres (78 miles)from the epicentre.
The operation of shinkansen bullet trains was suspended due to the quake, East Japan Railway announced.
Japan is one of the world's most seismically active countries, sitting on top of four major tectonic plates along the western edge of the Pacific "Ring of Fire".
It has strict construction regulations intended to ensure buildings can withstand strong earthquakes.
However, it is still haunted by the memory of a massive 9.0 magnitude undersea quake in 2011, which triggered a tsunami that left around 18,500 people dead or missing and caused a devastating meltdown at the Fukushima nuclear plant.
