A group of South Korean lawmakers on Tuesday visited an isolated set of islands at the centre of a territorial dispute with Japan -- prompting an immediate protest from Tokyo.
Seventeen members of the parliamentary National Defence Committee flew to the Dokdo islands (known as Takeshima in Japan) on military helicopters for a day-long visit, an aide to committee member Han Ki-Ho said.
The trip -- described as a government inspection session -- was aimed at checking security measures around the islands which are guarded by the South's coastguard, the aide told AFP.
A picture released by the committee showed the lawmakers shouting slogans with a placard reading "Dokdo is our land. We will defend it".
Japanese Chief Cabinet Secretary Osamu Fujimura, who on Monday had urged the Seoul MPs to cancel their trip, said it was "extremely regrettable" that his call had gone unheeded.
"We strongly protest it and we are urging South Korea to prevent future incidents," Fujimura told a regular media briefing Tuesday in Tokyo.
The islands, which lie between the two countries, are controlled by South Korea but claimed by both nations.
The longstanding row over ownership boiled over in August when South Korean President Lee Myung-Bak made a surprise visit to the islets.
Tokyo said the trip, the first ever by a South Korean president, was deliberately provocative.
Lee said it was designed to press Japan to settle lingering colonial-era grievances, including the issue of Korean women forced into sexual slavery for Japanese troops during World War II.
Japan colonised Korea from 1910 to 1945.
In August 2011 three conservative Japanese lawmakers tried to visit Ulleung island, the closest South Korean territory to the Dokdo/Takeshima chain, to voice their anger at Seoul's "occupation" of the islets.
South Korean immigration officers refused to allow them into the country, citing security concerns.
Japan is embroiled in a separate row with China over a different set of disputed islands in the East China Sea, which are also claimed by Taiwan.