A top United Nations official on human rights has met with a group of former South Korean "comfort women" who were forced to work in Japan's military brothels before and during World War II

"I will endeavor to continue to advocate on their behalf," U.N. High Commissioner for Human Rights Zeid Ra'ad Al Hussein said Wednesday during the meeting, held at a Seoul museum dedicated to promoting women's rights, according to Yonhap News Agency.

"I will, of course, stay in touch with them and visit them again as often as I can," he added.

Zeid became the first U.N. human rights chief to visit South Korea and meet with former comfort women, according to the South Korean Foreign Ministry.

The high commissioner for human rights arrived in Seoul on Tuesday for a three-day visit. On his first day, he attended the opening of a U.N. field office in the South Korean capital for monitoring and studying the situation of human rights violations in North Korea.

The comfort women issue remains one of the biggest stumbling blocks in improving ties between South Korea and Japan.

At talks held on Sunday in Tokyo, South Korean Foreign Minister Yun Byung-se and Japanese Foreign Minister Fumio Kishida remained at odds over the issue, which involves Korean women and several other nationalities.

South Korea has demanded that Japan settle the issue in a way that's acceptable to the women who are still alive, such as by issuing an apology and providing compensation.

But Japan maintains that all compensation issues were settled under the 1965 bilateral treaty that normalized diplomatic ties.