Rights groups are determined to keep Nobel Peace Prize winner Liu Xiaobo in the international spotlight despite China's efforts to stop the detained activist getting recognition.

One group of international lawyers has petitioned a UN human rights panel hoping to get Liu's detention declared against international law. Rights groups have showered awards on him and other Nobel prize winners have appealed for his release.

But few see any early signs of hope for the release of the 54-year-old literary critic, as China refuses to let his family attend the December 10 award ceremony and lobbies other countries to boycott the event.

Lawyers working on Liu's behalf registered a petition with the UN Working Group on Arbitrary Detention on November 4.

The prison term being served by Liu and the house arrest imposed on his wife, Liu Xia, "shocks the conscience," said Maran Turner, executive director of Freedom Now, the group providing the lawyers for the Nobel winner.

Liu was jailed for 11 years in December 2009 on subversion charges after co-authoring Charter 08, a petition calling for political reform. His wife has been put under house arrest in Beijing.

The UN working party will send the petition to the Chinese government which can refuse to make a response, said Beth Schwanke, a spokeswoman for Freedom Now. China has said that the award was "encouraging crime."

"Certainly the working group will have a favorable opinion and will establish that the conviction and the detention of Liu Xiaobo are in violation of international law," Schwanke told AFP.

"Our opinion is that the Chinese government has no legal basis under the international law to condemn and detain Liu Xiaobo," she added.

The working group's opinion will be made public. "That will be further reason for the Chinese government to release Dr. Liu," said Schwanke.

No one knows how long the process will take however.

Jerome Cohen, a New York University law professor who is on the team of lawyers, said dozens of cases involving detainees in China have already been put to the UN working group.

"It has almost always decided that detention is arbitrary," Cohen said. "It will most likely be the case this time.

"But even if they do it, of course there is not very much to expect," added Cohen, who called Liu's detention and sentencing arbitrary. "It will just be another signal."

International PEN, the writers' group is also stepping up activities for Liu. The German branch of the group awarded him its top prize. Human Rights Watch gave its Alison des Forges award to Liu last month.

Fifteen other Nobel Peace Prize winners sent a letter to UN Secretary General Ban Ki-moon and leaders of the Group of 20 economic powers to put pressure on China, a member of the group which recently held a summit.

But there was no mention of Liu's case at the G20 summit in Seoul this month and the UN leader, like many heads of government, has been extremely prudent in his comments on Liu's Nobel victory.

The UN petition will have greater effect on the West than it will China, said Marie Holzman, head of the French non-government group Solidarite-Chine.

"It is excellent for making Western public opinion aware that China is only a big economic power and that human rights there are thwarted," said Holzman.

"I do not expect any impact on the Chinese government, but this petition, like the Nobel Prize award, will have an impact on the West's conscience," she said.