The Japanese government only officially apologised to former American POWs five years ago, and Mitsubishi's initiative yesterday appeared to be the first of its kind by a Japanese corporation.
Senior Mitsubishi executive Hikaru Kimura presented a "most remorseful apology" to 94-year-old James Murphy of California, one of just a few surviving US prisoners forced to work in Japan.
Murphy accepted the "sincere, humble" apology.
"For 70 years since the war ended, the prisoners of war who worked for these Japanese companies have asked for something very simple, they asked for an apology," he said.
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Kimura and other company representatives met earlier with Murphy and families of other former POWs "to express our most remorseful apology for their being subjected to hard labour during World War II, when they worked in mines operated by Mitsubishi," he said.
Speaking through a translator, Kimura noted that close to 900 POWs were assigned to hard labour at four mines in Japan.
Thousands of other US prisoners were pushed into slave labour at Japanese firms during the war.
"As the company that succeeded Mitsubishi Mining, we cannot help feeling a deep sense of ethical responsibility for this past tragedy."
The apology was made during a ceremony at the Simon Wiesenthal Centre's Museum of Tolerance in Los Angeles. The centre is dedicated to the rights of Holocaust survivors.