The operator of a stricken nuclear power station said radiation levels in seawater near the plant had risen, a news report said Saturday, dpa reported.
Tokyo Electric Power Co (TEPCO) said the company found on Thursday 110 becquerels of radioactive iodine-131 per cubic centimeter in seawater samples collected near the northern part of the Fukushima Daiichi Nuclear Power Plant, which was crippled by the March 11 earthquake and tsunami.
The figure is 2,800 times higher than the legal limit. At the same spot, the operator detected 600 times the standard Tuesday and 1,000 times Wednesday, public broadcaster NHK said.
The operator also found a reading 9.3 times the limit off the coast of Minami-soma City, 15 kilometres north of the plant.
The government's Nuclear and Industrial Safety Agency instructed TEPCO to review its monitoring activities, NHK reported. The radioactive material was likely to be carried northward by ocean currents, NHK reported citing the agency.
The agency stressed the need to reinforce the operator's monitoring in areas with high concentrations of radiation to clarify possible contamination of the ocean, NHK said.
The official death toll from the March 11 disaster stood at 12,750 with 14,706 people listed as missing, Japan's National Police Agency said.