SEOUL - Japan should avoid aggravating historical tensions in a diplomatic row over Republic of Korea (ROK) forced to work for Japanese firms during World War Two, ROK's foreign ministry has warned. 

ROK's top court ruled last month that Japan's Nippon Steel & Sumitomo Metal Corp must compensate four ROKs for their forced labour during the war, which Japan has denounced as "unthinkable" 

ROK's top court ruled last month that Japan's Nippon Steel & Sumitomo Metal Corp must compensate four ROKs for their forced labour during the war, which Japan has denounced as "unthinkable." 

The binding court verdict is straining relations between the neighbours and could affect bilateral efforts to rein in the Democratic People's Republic of Korea (DPRK)'s nuclear programme, analysts say. 

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Japan and ROK share a bitter history that includes Japan's 1910-45 colonisation of the Korean peninsula and the use of comfort women, Japan's euphemism for girls and women, many of them Korean, forced to work in its wartime brothels. 

Japan's Foreign Minister Taro Kono said in a Bloomberg interview on Sunday that "it would be difficult for any country to do anything with the South Korean government" if a court can reverse Seoul's agreements made under international law. 

The Republic of Korea is also referred to as South Korea. 

Kono's remarks threatened to add fuel to the controversy, ROK's foreign ministry said late on Tuesday. 

"South Korea is very concerned that Japan's leaders in positions of responsibility are disregarding the root cause of the issue...and continue to make comments that rouse our public's emotions," the ministry said in a statement. 

"The Japanese government must be clearly aware that excessive political emphasis on the present case will be of no help to the future-oriented relationship between South Korea and Japan," the ministry added. 

The row was triggered by a Supreme Court ruling that Nippon Steel pay 100 million won (US$87,700) to each of the four steel workers who sought compensation and unpaid wages, saying that their rights to reparation was not terminated by a 1965 treaty. 

Japan says the issue had been resolved "completely and finally" by the 1965 agreement. 

Chief Cabinet Secretary Yoshihide Suga said on Wednesday ROK was in violation of international law after the Supreme Court issued its verdict, and Seoul should take steps to redress the situation immediately. 

"We are watching to see what concrete steps the South Korean government will take," Suga said. 

A senior official in ROK's presidential office said on Wednesday the government needed time and Japan's latest comments were not helpful. 

"There has been a ruling by the judiciary that differs from the previous government stance, so we have to arrange our stance," said the official, who declined to be named. 

"This takes time, and the Japanese government overly criticizing our government does not help resolve the situation," the official added. 

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ROK says there were nearly 150,000 victims of wartime forced labor, 5,000 of whom are alive. Japan says the compensation issue was settled by the 1965 treaty normalizing ties. 

In December, a ROK  appeals court is expected to rule on a similar case of compensation claims against Mitsubishi Heavy Industries.