The WTO's highest court overturned an earlier judgement from 2018, handing Seoul a final victory in a legal battle that has dragged on for years.

"Even though the ruling did not acknowledge that South Korea's measures comply with the WTO rules, it is extremely regrettable that Japan's argument was not approved," said the foreign ministry in Tokyo.

"There is no change in Japan's position of demanding South Korea lift all the restriction measures, and we will pursue this via talks with South Korea," added the ministry in a statement.

Foreign Minister Taro Kono urged South Korea to "correct its policy" but acknowledged that Japan had now run out of legal recourse.

Fearing radioactive contamination, Seoul imposed a partial ban on seafood imports from the region after the 2011 earthquake, tsunami and nuclear meltdown at the Fukushima Daiichi plant.

Tokyo first took the row to the WTO in May 2015, requesting consultations -- the first step under the global trade body's settlement system.

But talks broke down, prompting Japan to seek a WTO ruling in August 2015.

The WTO panel ruled in 2018 that South Korea should lift its ban but the so-called appellate court quashed this, the final word on the subject.

According to Fukushima authorities, four countries and regions -- China, Hong Kong, Taiwan and Macau -- have maintained a ban on importing a broad range of locally-produced foods.

South Korea, Singapore, the United States and the Philippines have partial bans in place.

But the majority of other countries and regions -- including the European Union -- have lifted bans on imports or allow imports on condition that a certificate of inspection is attached.