The Nuclear Regulation Authority proposed Wednesday raising the severity status of the recent radioactive water leak from a tank at Tokyo Electric Power Co.'s Fukushima No. 1 nuclear plant to level 3 from an earlier level 1 on the International Nuclear and Radiological Event Scale (INES).

The level 3 rating corresponds to a "serious accident" while the level 1 designation means an "anomaly," according to the eight-level rating system.

The NRA said about 300 tons of highly radioactive water has leaked from tank No. 5 in the H4 area of the damaged plant. In total, it said, the nuclear materials released into the environment has been estimated at several thousand terabecquerels, converted into radioactive molybdenum 99.