The Meteorological Agency on Sunday raised the volcanic alert for Shinmoedake in the Kyushu region to Level 3 from Level 2.
The agency warned that large volcanic rocks could reach areas within 4 kilometers of the crater of the volcano, which is located between Miyazaki and Kagoshima prefectures.
Level 3 urges restrictions on entry to the volcano, while Level 2 advises people to avoid approaching areas around the crater.
At Shinmoedake, volcanic earthquakes have increased since around Friday, and changes believed to be the swelling of the mountain have also been confirmed, according to the agency.
The alert for Shinmoedake was raised to Level 2 on Dec. 12 last year from Level 1, which warns of a possible increase in volcanic activity.
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