The Japan Meteorological Agency issued an eruption warning of Mount Io in southern Japan on Sunday, Sputnik reported.
Experts observed an increase in volcanic earthquakes in the Kirishima mountain range on Kyushu island, urging tourists and hikers to avoid the 0.6-mile area around Mt. Io's crater.
The agency said at least 37 volcanic tremors have been recorded at the site by mid-Sunday.
Intensified activity around the 4,300-foot volcano dates back to July 2015.