A hundred South Korean victims of Japan's forced labor during World War Two joined damages claim lawsuits against Japan's "war criminal" companies, filed in April 2015 by 1,004 other victims.

The Asia Victims of the Pacific War Family of the Deceased Association of Korea, which advocates the forced labor victims and their bereaved families, held a press conference in central Seoul on Tuesday, announcing their decision.

The advocacy group said it will continue to find other victims to encourage them to join the class-action suit and receive damages from Japan's war criminal companies.

In April last year, the association gathered 1,004 South Korean forced labor victims and their bereaved families to file the biggest-ever class-action lawsuit against the Japanese companies.

The victims, who were forced into hard labor for Japan's war munitions factories during the devastating war, sued some 70 Japanese firms, including Nippon Steel and Mitsubishi Heavy Industries, for unpaid wages and damages, demanding a total of about 100 billion won (90 million U.S. dollars) in damages.

The number of victims participating in the class-action lawsuit gained from 252 in April 2014 to 1,004 a year later, before rising to 1,104 in February this year.

    Despite the filing, the trial has yet to open in a South Korean court as the Japanese companies declined to attend the trial for nearly three years.

The victims urged the court to open the trial in the absence of Japanese firms to conclude the case.

South Korean historians say at least 700,000 young Koreans were lured into hard labor by the Japanese firms, claiming that they would be allowed to go to school in return for work during the 1910-1945 Japanese colonial rule of the Korean peninsula.

Japan's war criminal enterprises have insisted that the damages claim was settled in a 1965 treaty that normalized diplomatic ties between South Korea and Japan, but the South Korean victims said individual right to claim damages should be treated separately from the inter-governmental agreement.