South Korea's top court ruled on Thursday that Japan's Mitsubishi Heavy Industries must compensate 28 South Koreans for forced labour during World War II in a ruling that drew an immediate rebuke from Tokyo.

The decision echoed the Supreme Court's landmark verdict last month that ruled in favour of South Koreans seeking compensation from Japan's Nippon Steel & Sumitomo Metal for their wartime forced labour.

The court upheld a 2013 appeals court decision that Mitsubishi must pay 80 million won ($71,000) in compensation to each of the 23 plaintiffs.

In a separate ruling, the court also ordered Mitsubishi to pay up to $134,000 to each of five plaintiffs or their families.

'Deeply regrettable'

Mitsubishi called the verdict "deeply regrettable", saying in a statement it would discuss its response with the Japanese government.

Japanese Foreign Minister Taro Kono issued a statement condemning the court's decision, which he said was unacceptable.

"This fundamentally overturns the legal basis for friendly ties between Japan and South Korea and is extremely regrettable," Kono said.

The five former labourers had previously tried legal action in Japan, but their cases were dismissed on the grounds that the South Koreans right to reparation was terminated by a 1965 treaty that normalised diplomatic ties between the two countries.

However, the South Korean Supreme Court upheld last month's ruling that Japan's occupation of the peninsula was illegal.

"The treaty does not cover the right of the victims of forced labour to compensation for crimes against humanity committed by a Japanese company in direct connection with the Japanese government's illegal colonial rule and war of aggression against the Korean Peninsula," the court said in a statement.

'I feel great'

Kim Seong-ju, a 90-year-old plaintiff in the second case, said she was sent to Japan when she was 15 with the recommendation of her teacher, who was a Japanese national.

"I was told that I could go to middle and high school and study more, but it turned out I had to work at the factory all the time," Kim told a news conference after the ruling, showing her permanently injured hand. "Now I feel great."

Japan and South Korea 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 military brothels.

The rows over wartime history have long been a stumbling block for relations between the East Asian neighbours, sparking concern their joint efforts to rein in North Korea's nuclear programme could be affected.