A volcano northwest of here erupted on Tuesday, the Japanese Met office said, triggering a nearby avalanche. Some 15 persons were injured in the eruption, while four were caught in the avalanche.

Mount Kusatsu-Shirane in Gunma erupted triggering the avalanche in the neighbouring Kusatsu International Ski Resort in Kusatsu-machi, a firefighter involved in rescue operation told Xinhua news agency.

The Japan Meteorological Agency (JMA) said smoke was initially seen rising from the south side of the volcano and a volcanic tremor with a large amplitude was also observed.

Then rocks were seen falling from the site of the volcano. The JMA raised its warning for Mt. Kusatsu-Shirane to level 3 on its scale.