The city assembly of Tsushima, Nagasaki Prefecture, adopted a unanimous resolution Thursday demanding the South Korean city of Masan repeal its ordinance that claims Japan's Tsushima Islands as South Korean territory.

In March 2005, the municipal assembly of Masan in South Gyeongsang Province designated June 19 as "Daemado Day," commemorating the dispatch of Korean forces to Tsushima on that day in 1419. The Japanese islands lying between the two countries are known as Daemado in Korean.

Although Tsushima has stayed silent over the matter, some assembly members have begun voicing their concerns amid strained bilateral ties between Japan and South Korea in part over former Prime Minister Junichiro Koizumi's visits to the war-linked Yasukuni Shrine, assembly members said.

Masan's ordinance came as a tit-for-tat step shortly after the Shimane Prefectural Assembly in March 2005 designated Feb. 22 as "Takeshima Day" to press Japan's claims to South Korean-held rocky outcroppings known by the South as Dokdo, stirring outrage in South Korea.

The two small islets, with a total area of 0.23 sq. km, has had a South Korean Coast Guard post there since 1954.

Some Tsushima assembly members have been cautious about their resolution, however, hoping it will not further complicate bilateral strains, they said.

The Masan ordinance says it is designed to have people at home and abroad recognize that Tsushima is South Korean territory with common historic and cultural backgrounds and hence a territorial right, but the Japanese city sees no historical grounds in the claim, city officials said.

The Tsushima resolution says the claim in the Masan ordinance is groundless and an imprudent view.

One city official expressed concern that the assembly's move may have a negative impact on tourism to the islands.