SEOUL, South Korea — Kim Bok-dong, a former sex slave for the Japanese military during World War II whose tireless campaigning helped bring international attention to the suffering that thousands of women like her endured, died on Monday in Seoul. She was 92.

Ms. Kim had cancer. Yoon Mi-hyang, president of the Korean Council for Justice and Remembrance, an advocacy group for the South Korean women who were forced to work in Japanese brothels, announced her death, at Severance Hospital, on Tuesday.

Since the early 1990s, Ms. Kim had been a prominent representative of the former sex slaves, who were known euphemistically as comfort women. She was one of the first to break decades of silence and talk about what had been done to her, and she traveled around the world to testify about it, including at the United Nations.

To her last days, she demanded reparations from Japan. When reporters visited her in the hospital, she accused Prime Minister Shinzo Abe’s government of refusing to atone properly. Historians say as many as 200,000 girls, from Korea and other Asian countries, were forced or lured into sexual slavery during the war.