South Koreans who say they or their family members were forced to work for Japanese companies during World War II have sued Japanese firms, including Mitsubishi Materials Corp., their lawyers said.

Also covered by the suits involving 54 plaintiffs, which were filed Monday, are Mitsubishi Heavy Industries Ltd., Nippon Coke & Engineering Co., Sumiseki Holdings Inc., Nippon Steel Corp., JX Nippon Mining & Metals Corp., Nachi-Fujikoshi Corp., Nishimatsu Construction Co. and Hitachi Zosen Corp.

The suits were filed at the district court in Gwangju. They follow a similar move earlier in April by 31 South Korean plaintiffs at a Seoul court against four Japanese companies, including Nippon Coke & Engineering, which was formerly Mitsui Mining Co.