U.N. human rights agencies have pledged to try and help secure the repatriation of Sin Suk-ja and her daughters who are believed to be detained at a political prison camp in North Korea.

On Friday, Sin’s husband, Oh Gil-nam, visited U.N. headquarters in New York and submitted a letter asking for help for his family's release and repatriation.

U.N. officials promised to take necessary measures. Oh then proceeded to hold a protest outside North Korea's U.N. Mission in New York. He tried to hand a petition letter to North Korean Ambassador Sin Son-ho, but the ambassador rejected it.

Oh and Sin left South Korea for the North in the 1980s with their daughters but became disillusioned with life there. Oh later managed to escape the country but his wife and daughters were put into a prison camp.

Sin is nicknamed the "daughter of Tongyeong,” as she was born and raised in Tongyeong, South Gyeongsang Province.