BOSTON (Reuters) - A Chinese music student went on trial on Monday on U.S. charges that he harassed an activist who posted fliers at the Berklee College of Music in Boston supporting democracy in China and threatened to report her activities to Chinese law enforcement.

Assistant U.S. Attorney Alathea Porter told a federal jury in Boston that Xiaolei Wu, 25, scared the activist, referred to only as Zooey in court, by making threats online to chop off her hands and report her to the Chinese government because of her “reactionary posters.”

“She was afraid for herself, and she was afraid for her family, who was back in China,” Porter said in her opening statement to a 12-person jury.

The trial comes as U.S. and Western authorities continue to warn that China’s government has increasingly exerted pressure to silence its critics abroad.