SEOUL - Fifteen South Korean lawmakers on Tuesday left for a set of South Korea-controlled islets claimed by Japan in the latest development in the decades-old territorial dispute, the parliament's national defense committee said.

The lawmakers, all members of the defense committee, left Seoul at around 12:30 pm local time for the rocky East Sea islets by helicopter, said sources with the committee.

Japan, which describes South Korea's control of the islets as "illegal occupation", had warned against the trip, with Chief Cabinet Secretary Osamu Fujimura on Monday calling the planned visit "regrettable".

The sparsely inhabited islets, known as Dokdo?in South Korea?and Takehima in Japan, have been a chronic source of diplomatic row between the two Asian neighbors.

The acrimony surrounding the dispute reached a peak after South Korean President Lee Myung-bak's high-profile visit in August to the islets prompted fierce Japanese protests.

South Korea regained its control of the islets following the end of the 1910-45 Japanese occupation of the Korean Peninsula.

With the two countries long at odds over historical issues, many South Koreans see the recurring territorial disputes as a sign of an unrepentant Japan.