SEOUL, April 23 (Xinhua) -- The number of surviving South Korean victims to Japan's wartime sex slavery fell to 28 as another one passed away Monday.

Choi Duk-nye died of old age at the age of 97, according to the Korean Council for the Women Drafted for Military Sexual Slavery by Japan, a local advocacy group supporting the victims.

The bereaved families of the "comfort women" victim asked her life and burial service not to be disclosed to media, the advocacy group said.

"Comfort women" is a euphemism for girls and young women who were kidnapped, coerced or duped into sex servitude for Japanese military brothels before and during World War II.

With Choi's death, the number of surviving South Korean victims fell to 28 among 238 women who had identified themselves as former sex slaves.

In 2018 alone, four aged South Korean victims died.