Gao Yu's detention comes a month ahead of the 25th anniversary of the Tiananmen Square protests. She was reported missing on April 24, with friends presuming government officials had detained her.
Her lawyer, Teng Biao, spoke to the BBC about the confidential document that led to her arrest. He speculated that it could have been "Document Number 9," which reportedly details the government's plan to push economic reforms while controlling ideology and the spread of democratic ideals.
On Thursday morning, state-run CCTV showed a video of a woman identified as Gao publicly apologizing for her actions. With her face blurred, the woman said, "I admit that what I've done touched on legal issues and threatened national interests. My actions were very wrong. I have sincerely learnt my lesson, and I admit my guilt."
Chinese activists are routinely detained by authorities as significant anniversaries approach. And the 25th anniversary of the Tiananmen Square protests, which culminated with the deaths of hundreds (if not thousands) of students on June 3-4, 1989, is the topic of debate and introspection, although the government has banned public discussion of the topic.
Chinese authorities detained a number of activists on Tuesday, all of whom had attended a Saturday seminar on the Tiananmen protests.