The warning came after a quake measuring 6.8 on the Richter scale hit near the Fukushima nuclear site on Saturday morning.

Seismologists believe the strong tremor was an aftershock of the 2011 destructive earthquake in the eastern Asian country.

The US Geological Survey (USGS) said that the epicenter of the 6.8-magnitude quake, which was measured at a depth of 10 km (6 miles), was an ocean area located 131km (81mi) east of Iwaki city on the Japanese island of Honshu.

The earthquake caused a minor tsunami and prompted evacuation advisories for people living in the affected regions. However, the Japanese authorities later lifted all weather warnings.

Experts estimated that the quake was a delayed tectonic reaction to the 2011 earthquake that triggered a meltdown crisis at the Fukushima nuclear plant.

Seismologist Yasuhiro Yoshida of the Japan Meteorological Agency said that despite a steady decline in the activity of aftershocks, “they will still occur.”

"There are fears that relatively large earthquakes will occasionally occur in the ocean area where aftershocks of the great earthquake continue," he added.

On March 11, 2011, Japan was struck by a magnitude 9 earthquake, followed by a devastating tsunami that ravaged the country's northeastern coast. The tremor triggered a nuclear crisis by knocking out power to cooling systems at the nuclear power plant.

MA