South Korean President Lee Myung-bak says the safety of four Japanese lawmakers cannot be assured if they go ahead with a planned visit to an island claimed by both countries.

Mr. Lee's spokesman said Wednesday the president told officials to convey that message to Tokyo and to urge the Japanese to cancel the visit. The instructions were issued Tuesday at a weekly meeting with Prime Minister Kim Hwang-sik.

The spokesman did not say what sort of danger might confront the Japanese legislators, who say they intend to visit the island of Ulleungdo in waters between the two countries. The announcement sparked public fury in South Korea, where the trip is seen as an attempt to assert Japanese authority over islands now under South Korean control.

South Korean officials have said the Japanese may be turned back at Kimpo International Airport in Seoul if they attempt to go ahead with the trip.

Ulleungdo is the administrative headquarters for the disputed islands, known in South Korea as Dokdo and in Japan as Takeshima. The islands have been under effective South Korean control since the end of Japanese colonial rule after World War II.

Long-simmering tensions over the islands came to a head after South Korea's flag carrier Korean Air passed over the islands during a demonstration flight of its new Airbus A380 super-jumbo airliner last month.

Japanese officials decried the flight as an infringement of Japanese air space and banned foreign ministry officials from using the Korean airline for a month.