Mount Aso in southern Japan has sent huge plumes of grey smoke as high as 11 kilometres (6.8 miles) into the air in one of the volcano's biggest explosions in years.
The Japan Meteorological Agency says early Saturday's explosion also blew off bits of volcanic rock and ash, and raised the alert level for the area, extending the entry ban from just around the volcanic mouth to the mountain itself.
Nobody lives in the area and there were no reports of injuries or damage in the area still recovering from deadly earthquakes earlier this year.
Mount Aso has repeated smaller eruptions in recent years. The agency said the volcano could erupt again.
Japan sits atop the Pacific "ring of fire" and has more than 100 volcanoes.
The Japan Meteorological Agency says early Saturday's explosion also blew off bits of volcanic rock and ash, and raised the alert level for the area, extending the entry ban from just around the volcanic mouth to the mountain itself.
Nobody lives in the area and there were no reports of injuries or damage in the area still recovering from deadly earthquakes earlier this year.
Mount Aso has repeated smaller eruptions in recent years. The agency said the volcano could erupt again.
Japan sits atop the Pacific "ring of fire" and has more than 100 volcanoes.