The country is now on red alert after a spike in seismic activity at Sakurajima, a volcano 30 metres higher the Mount Snowdon.
More than 600,000 citizens of Kagoshima, in southwestern Japan, have been told to flee their homes in fear of devastation
The Japanese Meteorological Agency said: “The possibility for a large-scale eruption has become extremely high for Sakurajima.”
It warned residents to exercise “strict caution” and prepare for evacuation.
“The possibility for a large-scale eruption has become extremely high.”Japanese Meteorological Agency
An official told Sky News: “There is the danger that stones could rain down on areas near the mountain's base so we are warning residents of those areas to be ready to evacuate if needed."
The huge volcano, which sits just 31 miles from the Sendai Nuclear Power Plant, erupted two years ago killing 63.
More than 1,600 died and 300,000 were evacuated after a colossal earthquake and tsunami battered the Fukushima Daiichi Nuclear Power Plant in 2011, the second worst nuclear disaster in history.
The Sendai plant was only restarted last Tuesday after Japan shut down all reactors in the wake of the Fukushima Nuclear Disaster.
The level four warning - the second highest on the scale - comes days after Japan commemorated the deaths of more than 150,000 people killed by nuclear bombs dropped on Hiroshima and Nagasaki.
Critics had warned Japan’s nuclear reactors are still vulnerable to natural disaster.
The Japanese weather agency warned another volcano, Ioyama, near to Sendai plant was at risk of eruption last October.
Japan is on the 'Ring of Fire' around the Pacific Ocean, where the Earth's huge tectonic rub together causing massive earthquakes and volcanos.
It has more than 100 active volcanoes, making it one of the most seismological volatile places on earth.