The UN High Commissioner for Human Rights met with three aging former "comfort women" on a visit to Seoul on Wednesday and promised to continue advocating on behalf of South Korean victims of Japan's wartime system of sex slavery.

Zeid Ra'ad Al Hussein met with the three, who are among some 50 surviving South Korean "comfort women", at a museum in Seoul dedicated to the women forced into sexual slavery during World War II.

Al Hussein would "continue to advocate on their behalf", he was quoted as saying by Yonhap news agency after the meeting.