South Korea issued a formal protest to Japan on Friday after Tokyo conducted a controversial opinion poll that asked citizens their views on a set of islands disputed between the two countries.
The public survey of 3,000 people, released Thursday, showed that six out of 10 Japanese view the Seoul-controlled islands in the Sea of Japan (East Sea) as their country's territory.
"Our government sternly protests Japan's renewed provocative actions," South Korea's foreign ministry said in a statement.
"We strongly urge Japan to stop such actions immediately," it said, adding that provocative remarks by some Japanese leaders are also posing "a serious obstacle" to the constructive development of bilateral ties.
The islands, known as Dokdo in Korean and Takeshima in Japanese, have been the subject of a bitter and decades-old territorial dispute that flared last year.
Though they are key trading partners, relations between the two countries have been regularly strained by a diplomatic discord over Japan's wartime aggression in Korea and the territorial dispute.
Many South Koreans believe Japan has failed to atone for abuses during the 1910-1945 colonial period which remains a constant source of tension.