The outspoken Chinese political analyst and journalist Gao Yu has been detained by Beijing police in a criminal investigation over charges of leaking state secrets abroad, weeks before the 25th anniversary of the military crackdown on the Tiananmen Square democracy movement. Gao, 70, leaked a secret document to editors of a foreign website in August last year, the official Xinhua news agency said on Thursday. Gao was “deeply remorseful” of her actions and “willing to accept legal punishment”, the report said, ending speculation over her whereabouts two weeks after she disappeared. China's national broadcaster CCTV aired her confession in an early morning news programme on Thursday, blurring out her face but showing her full name. Watch: Gao Yu's confession for "leaking state secrets" “I think my actions have touched on legal issues, have harmed the national interest," she tells a policeman. "What I have done was very wrong. I seriously and earnestly accept to learn a lesson and plead guilty." Gao's disappearance was noted last week when she did not attend a private meeting to commemorate the Tiananmen Square anniversary in Beijing as expected on April 26. She was detained on April 24, Xinhua said. Gao joins a growing list of pro-democracy activists and intellectuals who were rounded up ahead of the sensitive anniversary. Prominent human rights lawyer Pu Zhiqiang and four others have also been detained on suspicion of “picking quarrels and provoking trouble”. The move is indicative of authorities' wariness ahead of the sensitive occasion, said Maya Wang, a Hong Kong-based researcher with Human Rights Watch. “The authorities appear to want to, at the very least, put these people out of action before June 4, and secondly be heavy-handed to deter other activists from planning any commemoration events,” she said. The Xinhua report did not specify which secret document Gao allegedly leaked, but said she obtained the full document in June last year. The timing appeared to coincide with the leak of a confidential Communist Party circular that called on authorities to crack down on political dissent last year. Also known as Document No. 9, the circular warned of "political perils" including Western constitutional democracy, respect for human rights and media independence. Dated April 2013, the document was circulated among senior Party officials amid a series of arrests of outspoken rights activists and journalists. Xu Zhiyong, the founder of the New Citizen Movement, which calls for government transparency, respect for the constitution and equal access to education, was detained in July last year and has since been sentenced to four years in prison for "gathering crowds to disrupt public order". Gao began her career as a journalist with China News Service. She joined the progressive Economics Weekly as deputy editor-in-chief shortly before the Tiananmen Square democracy movement of 1989. The publication was shut down and she became one of the leading intellectuals to be arrested and jailed for their support of the movement. In 1993, she was re-arrested and a year later sentenced to six years in prison for leaking state secrets. Since her release in 1999, she has worked as a freelance writer and political commentator. Gao had planned to travel to Hong Kong to take part in a conference on May 3.