State news agency Kyodo reported Monday that an area within 4 kilometers (2.8 miles) of the primary crater of Mount Aso - the largest active volcano in Japan - was declared off-limits, while All Nippon Airways Co. had canceled six flights in the region and Japan Airlines Co. had canceled two.
Japan`s Meteorological Agency said that the eruption had occurred at around 9.43 a.m. (0043GMT) shooting ash 2,000m into the air and scattering large rocks.
It added that there was danger from falling rocks and smoke from the plume.
In Sept. 2014, a volcano erupted on the Japanese island of Honshu around 200 km (120 miles) southwest of Tokyo killing 57 people.
The Mount Ontake eruption was the first fatal volcanic eruption since the collapse of a lava dome at Mount Unzen in 1991, and the deadliest since Torishima killed an estimated 150 people in 1902.
Mount Aso - 1592m above sea level - has been erupting on and off since Nov. 2014.
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