Another Korean woman who was forced into sexual servitude by Japan's World War II soldiers died Sunday, a local advocacy group for former "comfort women" said, reducing the number of surviving Korean victims of sexual slavery to 40.

Yoo Hee-nam died at the National Medical Center in Seoul due to lung cancer, the House of Sharing said. The organization that runs the shelter for former sex slaves, euphemistically called comfort women, on the outskirts of Seoul, added Yoo's death lowered the number of known survivors to 40, among the 238 victims who are registered in the South Korean database.

Yoo was captured by Japanese soldiers at age 15 and brought to a brothel in Shimonoseki, Japan, before being tortured by soldiers there for a year. While Yoo was in the process of being moved to Singapore, the Japanese surrendered, and she returned home with the help of an Osaka resident.

After Korea's independence, Yoo made her living as a peddler, but she constantly suffered from insomnia and heart disease, the group said. Although she was diagnosed with lung cancer in 2009, she joined the House of Sharing and engaged in various activities to recover their honor and get an apology from Japan.

Last July, Yoo, along with another former comfort woman Kim Kyung-soon, lodged a lawsuit in a San Francisco regional district against Japanese Prime Minister Shinzo Abe, Japanese firms that enslaved Koreans for forced labor during the war and the Sankei Shimbun, a conservative Japanese newspaper, which has called former comfort women "prostitutes" in its articles.

Yoo also criticized the Seoul-Tokyo agreement on the issue of former comfort women that was reached last December, saying it didn't contain the victims' consent. The House of Sharing said Yoo is survived by a son and three daughters. Her funeral will be held Tuesday, it added. (Yonhap)