Chinese dissident Fang Lizhi, a key figure in the pro-democracy movement behind the 1989 Tiananmen Square protests, has died in the United States, fellow dissident Wang Dan said Saturday.

Fang, an internationally renowned professor of astrophysics, was granted refuge at the US embassy in Beijing for one year following the protests and was forced into exile in 1990.

He was dismissed from his job as vice-president of the University of Science and Technology of China because of his fight for democracy and human rights and for publicly supporting the Tiananmen protests.

Wang, who also lives in the United States, said on his Facebook page that Fang's wife had informed him of her husband's sudden death in Tucson, Arizona. Wang confirmed the death in an email to AFP.

Wang wrote that Fang, who was 76, "had inspired the '89 generation and awoke in the people their yearning for human rights and democracy."

Hundreds, perhaps thousands, are believed to have died when the Chinese government sent in tanks and soldiers to clear Beijing's Tiananmen Square on the night of June 3-4, 1989, bringing a violent end to six weeks of protests. An official verdict after the protests called them a "counter-revolutionary rebellion" although the wording has since been softened.