The exiled leaders of the 1989 Tiananmen Square pro-democracy movement and other Chinese dissidents have asked the government to allow them to visit their homeland, a rights group said.

"Because of political reasons we were denied renewal of our passports, had our passports revoked or were denied entry into China," Wang Dan, Wuer Kaixi, Hu Ping, Wang Juntao, Wu Renhua and Xiang Xiaoji wrote in a letter.

"In short, we have been deprived of our right to return to our country," they said in the correspondence dated Friday and released by the Human Rights in China group.

Wang Dan and Wuer Kaixi are two of the leading figures of the Tiananmen Square pro-democracy protests which were crushed by the army.

Hundreds, perhaps thousands, are believed to have died when the government sent in tanks and soldiers to clear the square in the centre of Beijing on the night of June 3-4, 1989, bringing a violent end to six weeks of pro-democracy protests.

An official verdict after the protests called them a "counter-revolutionary rebellion," although the wording has since been softened.

The exiled six appealed to Beijing to "abandon the old practices of not allowing people to return to their country because of differences in political views" and said they were willing "to discuss concrete ways to solve this problem".

Wang Dan was sentenced to four years' jail in 1991 but was released in 1993. In 1996 he was sentenced to 11 years for writings published abroad, before being released for "medical reasons" and sent to the United States ahead of a visit to China by then president Bill Clinton.

Wuer Kaixi, who is from the Uighur ethnic minority, managed to flee to Hong Kong and now lives in Taiwan.

Hu Ping is one of the main contributors to the dissident magazine "Beijing Zhi Chun" ("Beijing Spring").

Their letter coincided with the death Friday of fellow dissident Fang Lizhi in the United States at the age of 76.

Fang, an internationally renowned professor of astrophysics, was granted refuge at the US embassy in Beijing for one year after publicly supporting the Tiananmen protests. He was forced into exile in 1990.

Premier Wen Jiabao recently emphasised the need for "political reform" in China, pledging to give voters more choice at the village level.