Beijing is waging a campaign of harassment against Chinese activists who seek to testify at the United Nations about repression, while the world body sometimes turns a blind eye or is even complicit, Human Rights Watch said.

In a report released on Tuesday, the group said China restricts travel of activists, or photographs or films them if they do come to the U.N. in Geneva to cooperate with human rights watchdogs scrutinizing its record.

"What we found is that China is systematically trying to undermine the U.N.'s ability to defend human rights, certainly in China but also globally," said Kenneth Roth, executive director of Human Rights Watch.