China’s most prominent dissident has been arrested formally after more than six months in detention at a secret location near Beijing on charges that could bring a lengthy prison term.

Liu Xiaobo had been held virtually incommunicado under “residential surveillance”, being allowed only two visits from his wife, since he was taken from his Beijing home on December 8 – a day before publication of a document that he co-authored calling for democracy in China.

State media said: "Liu has been engaged in agitation activities, such as spreading of rumours and defaming of the Government, aimed at subversion of the State and overthrowing the socialism system in recent years." The arrest was made by the Beijing Public Security Bureau yesterday.

Mr Liu, along with a famed Taiwanese pop singer and two other intellectuals, joined the students in Tiananmen Square on June 2 in a hunger strike in support of their demand for greater freedom of speech and more democracy and to call for an end to corruption. He was with the students when tanks rolled into the heart of the city on the night of June 3 and 4 and helped to persuade the demonstrators not to make a stand and to leave the square without loss of life. Hundreds were killed elsewhere in the city in that crackdown.