The activist was being treated for terminal liver cancer in a hospital in north-eastern China.

He had been transferred from prison last month, where he was serving an 11-year term for "subversion".

A university professor turned tireless rights campaigner, Mr Liu was branded a criminal by authorities, and was repeatedly jailed throughout his life.

He was also subject to severe restrictions when not in prison, while his wife, Liu Xia, was placed under house arrest.

In the weeks leading up to his death, Mr Liu's case became mired in international controversy.

Several Western countries urged China to allow Mr Liu to leave the country to seek palliative care elsewhere. A German and an American doctor who recently visited and examined him in a hospital in Shenyang both said he would be able to travel abroad.

But Chinese medical experts insisted that he was too ill to travel.

In a brief statement on its website, the Shenyang legal bureau said that Mr Liu had suffered multiple organ failure, and that efforts to save the activist had failed.

Mr Liu was a pro-democracy figurehead for activists outside mainland China, although many of his compatriots were unaware of his struggles because the authorities rigorously censored news about him.

The activist played a significant role in the Tiananmen protests of June 1989 which ended in bloodshed when they were quashed by troops.

He and other activists negotiated the safe exit of several hundred demonstrators, and have been credited with saving the protesters' lives.

He was subsequently placed in a detention centre and released in 1991.