Police in northeastern China have arrested the leader of a signature campaign calling for improvements in human rights ahead of next year's Olympic games, a rights group said Tuesday.

Yang Chunlin was formally charged with "subversion of state power" last month in Jiamusi city, Heilongjiang province, China Human Rights Defenders said in a statement.

The main reason for Yang's arrest was a campaign to encourage thousands of local people to sign an open letter saying "we want human rights, not the Olympics", the group quoted his relatives as saying.

Police also told Yang's family that the charges against him included accepting funding from "overseas anti-China organisations".

Yang, a laid-off state worker, was detained at least four times last year for helping villagers with land disputes, the statement said.

Last month, about 40 leading rights activists and dissident writers signed an open letter appealing to China's communist leaders to uphold the Olympic spirit by allowing greater freedom.

The activists said they felt "disappointment and doubt as we witness the continuing systematic denial of the human rights of our fellow citizens even while - and sometimes because - Olympic preparations are moving forward".

Human Rights Watch and Amnesty International both released critical reports on China's human rights record last month as part of their pre-Olympic campaigns.