Despite the ongoing diplomatic tension over Japan's territorial claim to South Korea's easternmost islets of Dokdo, most mainstream Japanese scholars remain skeptical or cautious about the claim.

In its latest provocation, Japan's government on Tuesday referred to Dokdo as Japanese territory again in its 2011 defense white paper issued one day after a trio of Japanese lawmakers were denied entry at a Seoul airport due to their attempt to lay claim to the set of rocky outcroppings in the East Sea.

Hori Kazuo, an economics professor at Kyoto University, is among the Japanese scholars who do not agree with the Tokyo government.

In 1987, he found and unveiled to the public an ancient Japanese government document from 1877 clearly showing that Japan did not consider Dokdo as part of its territory back then.

The document then contained a directive from the Japanese Cabinet to Shimane Prefecture, the closest Japanese region to Dokdo, that it should keep in mind that the Korean islands of Ulleung and Dokdo have nothing to do with Japan.

Park Byeong-seop, a Korean-Japanese watcher of Dokdo, noted in his 2008 book titled "Dokdo-Takeshima Dispute" that even when Shimane Prefecture angered South Koreans in 2005 by establishing "Takeshima Day" to reassert Japan's claim to Dokdo, it did not post the claim on its official Web site. Takeshima is the Japanese name for Dokdo.

At the center of recent Japanese academic debates on Dokdo is the Japanese government's claim that in 1905 Japan occupied the uninhabited islets at the request of a fisherman in Shimane.

Ikeuchi Satoshi, professor of Nagoya University who has studied the Dokdo issue from a neutral point of view, said in a recent study published in a Japanese history magazine that the fisherman tried to contact Korea first to ask for exclusive rights to catch sea lions in the seas off Dokdo, an indication that the Japanese knew Dokdo belonged to Korea. The fisherman, however, did not actually carry out the plan.

The fisherman filed a civil complaint with the Japanese government asking that the islets be made part of the country's territory. The government initially rejected the request, the historian said.

In 1905, however, Japan unilaterally declared the Korean islets as part of its territory, putting Dokdo under the jurisdiction of Shimane.

He also said that Korean officials dismissed the territorial claims as "groundless" when Shimane residents visited Ulleung Island, the administrative base of Dokdo, in 1906 and informed them that Dokdo was now part of their region.

The diplomatic tension between Seoul and Tokyo resurfaced last month after the Japanese government took a punitive measure against Korean Air for flying a test flight over Dokdo. Tokyo ordered its diplomats to boycott Korean Air flights for one month from July 18 in protest over the test flight of the Airbus A380 in June.

Earlier this week, an ultra right-wing Japanese professor and three conservative opposition lawmakers were denied entry to South Korea before embarking on trips aimed at reasserting the claim to Dokdo through a visit to Ulleung Island. Ulleung is the closest South Korean territory to Dokdo.

South Korea rejects Japan's sovereignty claim over Dokdo as nonsense because the country regained independence from Japan's 36-year colonial rule in 1945 and reclaimed sovereignty over its territory, including Dokdo and many other islands around the Korean Peninsula. (Yonhap News)