The largest fisheries market in the South Korean capital is stepping up testing to show its offerings are safe, aiming to allay consumer concerns about Japan's planned release of treated radioactive water from the wrecked Fukushima nuclear plant.

The plan secured approval from the International Atomic Energy Agency (IAEA) this week, with the U.N. nuclear watchdog saying it met global safety standards and would have "negligible radiological impact" on people and the environment.

But there was just a scattering of visitors in the gleaming six-storey facility in Seoul, where teams of market officials pointed radiation detectors at fresh fish and seafood as they made random tests at 10 stalls, in hopes of reassuring buyers.