A Taiwanese labor relations professor has complained to the United Nations after a study group that she has regularly led was turned away from an International Labor Organization conference in Geneva this year.

Li-chuan Liuhuang of Chung Cheng University wrote an open letter to ILO director-general Guy Ryder noting her group has had access to the U.N.'s Geneva offices since 2014 for the International Labor Conference, but was refused entry twice this week during the two-week session that runs through Friday.

The episode highlights speculation about where and when China might seek to block Taiwanese interests in the international arena since independence-leaning President Tsai Ing-wen took office in Taiwan last month.

U.N. officials on Wednesday cited tighter security measures. A Chinese mission official had no comment.