The Foreign Ministry on Monday called in a Japanese diplomat to deliver its concern over a reported plan to discharge contaminated water from the site of the Fukushima nuclear power plant disaster.

Tomofumi Nishinaga, minister for economic affairs at the Japanese Embassy, was called in after claims were made by Greenpeace that Japan is planning to release over one million tons of radioactive water into the Pacific Ocean.

The Foreign Ministry delivered to the Japanese a document detailing South Korea's concerns and demanding Tokyo officially confirm or deny the NGO’s claim and explain how it plans to dispose of the water. 

According to the ministry, Nishinaga said he would relay Seoul's position to Tokyo. He added that Japan will faithfully and transparently offer information related to its handling of the water at the Fukushima plant.

The envoy was also cited as saying Tokyo is still reviewing how it will dispose of the contaminated water and when, adding that it has been working to expand the capacity of its storage facilities.

A nuclear specialist with Greenpeace recently warned in an article published in South Korea that the region will face increased radiation exposure if Japan discharges the water into the ocean.

Three reactors at the Fukushima nuclear power plant suffered meltdowns in a 2011 earthquake and tsunami. Since then, contaminated water from the plant has been stored in some one-thousand tanks onsite.