The Japan Meteorological Agency on Saturday started issuing volcanic activity warnings for areas centering around seven active volcanoes including one which is undersea in line with a revised meteorological business law, noting that there has been no change in the levels of activity themselves.

The areas subject to "warnings for crater adjacent areas" -- intended to give a warning as to the threat to life if one enters the area -- include Sakurajima Island in Kagoshima Prefecture and Miyakejima Island in Tokyo. The undersea Fukutokuokanoba area in the Pacific south of Izu Peninsula is subject to an eruption warning.

Public broadcaster NHK (Japan Broadcasting Corp.) is required to broadcast warnings to the public.

Separate from warnings, eruption alert levels in the scale of one to five with five representing the most serious have also been introduced for 16 volcanoes including Mt. Fuji. The highest was Level 2 given to Sakurajima in Kagoshima Prefecture, which was also given a warning. Level 2 advises restraint in approaching the crater.

Mt. Fuji was given a Level 1 warning, meaning no restriction to access.