The Korean Council for Women Drafted for Military Sexual Slavery by Japan said Yoon Geum-rye died on Friday at the age of 90, while another victim of Japanese sex slavery, known only by her family name Bae, passed away at 88 on Monday.

With their deaths, the number of South Korea's government-registered surviving victims of Japan's sexual enslavement, euphemistically called "comfort women," was reduced to 61, the council said.

The comfort women issue is becoming increasingly urgent as most surviving comfort women are well over 80 years old and may die before they receive compensation or an apology from Japan. A total of 16 victims passed away in 2011.

Japan, which colonized the Korean Peninsula from 1910 to 1945, has acknowledged that its wartime military used sex slaves. Tokyo refuses to issue an apology or compensate the victims individually, however, arguing that the issue was settled by a 1965 treaty that normalized relations between the two countries.

Since 1992, victims and their supporters have held weekly rallies outside Japan's Embassy in Seoul, demanding compensation and an apology from Tokyo. In December, they held their 1,000th protest and set up a bronze statue of a girl symbolizing the victims in front of the embassy.

Another rally is to be held later in the day, expressing condolences for the two deceased women, according to the group.

Yoon was taken to service the Japanese military in the Chinese city of Hunchun in Jilin province at the age of 20 and Bae was dragged into slavery on the island of Sumatra in Indonesia when she was only 17. Both returned home only after the end of the colonization. (Yonhap News)