TOKYO, Jan. 23 (Xinhua) -- Mount Kusatsu-Shirane in the northwest part of Gunma Prefecture, north of Tokyo, erupted on Tuesday morning, the weather agency here said.
Around 15 people were injured as a result of the eruption, local firefighters said.
According to the Japan Meteorological Agency (JMA), smoke was initially seen rising from the south side of the volcano and a volcanic tremor was also observed.
Rocks were seen falling from the site of the volcano, the JMA and local reports also said.
As a result of the eruption, the JMA raised its warning for Mount Kusatsu-Shirane to level 3 on its scale which peaks at 5, instructing people not to approach the volcano.
Mount Kusatsu-Shirane is a 2,160-meter active volcano with its summit located north of the Asama volcano.
It consists of a series of overlapping pyroclastic cones and three crater lakes.
The largest crater is Yu-gama, an acidic lake with a blueish hue. The surface of the lake has yellow sulfur floating on its surface.
The series of volcanic peaks are located just outside the town of Kusatsu Onsen, which is popular for walkers and hikers as well as those looking to enjoy natural hot springs.
