|From left to right, Tomomi Inada, Masahisa Sato, Yoshitaka Shindo, were repatriated from Seoul upon arrival [Reuters]
South Korea has summoned a senior Japanese envoy to lodge "a strong protest" after three opposition politicians from Japan attempted to restate their country's claim to a group of disputed islands.
The heightened diplomatic tensions came a day after the politicians were barred from entering South Korea upon their arrival in the capital Seoul early on Monday.
The members of parliament had planned to visit Ulleung island, the closest South Korean territory to the uninhabited disputed Dokdo islands in the Sea of Japan [East Sea], which are known in Japan as Takeshima.
The legislators from Japan's conservative Liberal Democratic Party had refused to fly back home for nine hours, before being repatriated in the late evening from Seoul's Gimpo International Airport.
Airport authorities stopped them from passing through immigration, citing a law which prohibits entry of anyone who could harm South Korea's national interests or public safety.
Seoul's foreign ministry said on Tuesday that the failed trip had "negative impacts" on relations and warned that the politicians would be sent back again if they stage a repeat visit as promised.
"We find it very regrettable that they did not properly respond to legitimate requests of our immigration officials to leave, defying our legal order and law enforcement," Cho Byung-Jae, a spokesman, told reporters.
The Japanese embassy official was also summoned in protest against the release on Tuesday of Japan's 2011 defence white paper, which describes the islands as Japanese territory.
In a statement, South Korea's defence ministry said: "The defence ministry urges the Japanese government to realise they can never expect progress in bilateral military relations without giving up a claim to Dokdo.
"We will respond resolutely to any attempt to violate our territorial rights."
One of the three Japanese politicians who were repatriated is Yoshitaka Shindo, the grandson of a general in the imperial Japanese army, who has previously accused South Korea of "illegally and militarily" occupying "what is undoubtedly our territory".
"We don't intend to fight there. We want to express our feeling of anger to the South Korean people," Shindo said in a video message posted on his website.
The other two legislators are Tomomi Inada, a former lawyer who denies the 1937 Nanjing massacre by Japanese troops in China, and Masahisa Sato, a former member of the military who headed a Japanese reconstruction mission to Iraq in 2004.
Shindo said at Gimpo airport on Monday that Dokdo rightfully belonged to his country.
"However, we must discuss the issues as there is a difference in opinion between Japan and South Korea," Shindo said, according to the South Korean Yonhap news agency. "If our entry is denied, we will visit once gain."
He said the entry ban might evolve into a diplomatic row between the nations.
Earlier, hundreds of South Korean protesters gathered at Gimpo airport to protest against the three legislators' arrival.
They carried banners which read "Stop Japan!" and "You die!", while other protesters carried a coffin plastered with photos of the politicians.
One group set fire to photos of the three, while others got caught in small scuffles with the police as they tried to enter a security area to "hunt down" the legislators.
The disputed islands are a sensitive issue for the South Koreans, especially for the older generations who still have bitter memories of Japan's harsh colonial rule over Korea from 1910 to 1945.
South Korea says it regained control over all of its territory, including Dokdo, at the end of the colonial period.
It posts a small coastguard force on Dokdo and has sought to strengthen its control over the islets after Tokyo in March authorised new school textbooks reasserting its claims to them.
In a rare showcase of solidarity with the South, North Korea condemned the Japanese legislators' actions.
"The Japanese reactionaries' recent moves are serious issues not to be tolerated by the Korean nation," a commentary on the official KCNA news agency said, accusing the three of trying to seize both Ulleung and Dokdo islands.