The volcanic alert level for Mount Kusatsu-Shirane in central Japan have been raised due to increased activity.

Japan's Meteorological Agency says the frequency of volcanic earthquakes on the mountain in Gunma Prefecture has increased from 7 on Saturday to 153 by 4 PM on Sunday.

The agency says there has been a slight change in ground elevation on the mountain from Saturday through Sunday evening.

The agency raised an eruption alert level to 2 on a scale of one to 5 on Sunday morning, citing the possibility of a fresh eruption affecting an area near a lake in the crater.

The agency advises caution amid the possibility of large rocks being expelled up to one kilometer, as well as ash, smaller rocks and gas being carried by the wind.

Kusatsu municipal officials have restricted entry into the area.

The Gunma Prefectural government has also closed an 8.5-kilometer section of a tourist highway linking neighboring Nagano Prefecture.

Source: Kyodo