The Peace Boat, a ship owned by a nongovernmental organization of the same name, and more than 500 passengers landed on Russian-held Kunashiri Island off Hokkaido on Tuesday morning -- despite a Foreign Ministry request that they not visit the disputed islet.

The group of 530, mostly young Japanese along with some South Koreans, Americans, German and Inuits, arrived aboard the ship and will be on the island until Wednesday. They will meet local people to exchange views on the relationship between Japan and the island, organizers of the trip said.

Some of the visitors will stay at a Japanese government-funded facility dubbed "Muneo House," after arrested Diet member Muneo Suzuki. His aide has been charged with rigging bids for building the facility formally known as the House of Friendship. Others will stay at homes of local residents, according to the group.

In Tokyo, Hatsuhisa Takashima, the Foreign Ministry's press secretary, expressed regret that Peace Boat passengers visited Kunashiri despite repeated efforts by the ministry to convince them not to.

"The (Japanese) government has been urging its citizens not to enter the Northern Territories like this . . . because doing so while the Russian Federation is illegally occupying the territories will make it appear as if they consider the land belongs to Russia," Takashima said in a statement.

Japan and Russia launched a visa-free exchange program in 1992 aimed at promoting ties between Japanese -- mainly former residents of the islands -- and the Russian inhabitants.

The Foreign Ministry maintains that the program should be organized by the government, and civil activities outside the program may obstruct bilateral negotiations over the islands, given the sensitive nature of the dispute.

Peace Boat's ship left Kobe on Aug. 15 with some 570 participants on a two-week trip to promote grassroots diplomacy. They visited North and South Korea and the Russian island of Sakhalin before reaching Kunashiri.

The group claims people-to-people diplomacy is necessary for improving relations between Japan and its neighbors. , and also for resolving the decades-old territorial row.

Peace Boat representatives in September 1991 visited Kunashiri as well as the Russian-held Etorofu and Shikotan islands, also without visas.

The three islands and the Habomai islets were seized from Japan by Soviet troops at the end of World War II. The long-standing territorial dispute has prevented Japan and Russia from concluding a postwar peace treaty.

The Foreign Ministry did not object to the group's action in 1991. But this time the ministry pressured the NGO and urged Russia not to permit the visit.

Prior to the launch of the visa-free exchange program, the government urged Japanese not to seek visas from the then Soviet authorities to visit the islands, as it believed such action would be tantamount to acknowledging Moscow's sovereignty over the territory.

On Monday, the Peace Boat organization protested the ministry's attempts to persuade Russia to block the visit.

Takayoshi Kise, a Peace Boat leader, said the ministry again pressured the group to cancel the visit.