China said Friday its relations with Norway remained "difficult", a year after it downgraded relations with Oslo in response to the award of the Nobel Peace Prize to jailed dissident Liu Xiaobo.

"The difficulties between China and Norway are because the Norwegian government made the wrong decision when the Nobel Peace Committee gave the award to Liu Xiaobo," Chinese foreign ministry spokesman Hong Lei said.

"We hope the Norwegian side will make practical efforts to resume the development of the bilateral relationship," he told reporters.

His remarks came as five Nobel Peace Prize winners launched a campaign to free Liu, saying they feared Beijing was silencing his family and friends and the world would forget his plight.

Liu, the first Chinese citizen to win the Peace Prize, was sentenced to 11 years behind bars in 2009 after authoring Charter 08, a manifesto signed by thousands seeking greater rights in the communist nation.

The decision to award him the Nobel infuriated Beijing, which suspended talks with Oslo on a free trade pact and ordered strict and time-consuming veterinary controls on Norwegian salmon.

The five members of the Norwegian Nobel Committee, who pick the Peace Prize laureate, are appointed by Norway's parliament, but are independent of the government and the legislature.

Hong, who made the comments ahead of Saturday's ceremony for the 2011 Nobel Peace Prize, did not elaborate on what measures Norway could take to restore ties.

Asked about the alleged illegal treatment of Liu's wife, who is under house arrest and has not been seen in public for a year, Hong insisted her case was being handled in accordance with the law.

Meanwhile a group of Chinese academics on Friday awarded Russian Prime Minister Vladimir Putin the Confucius Peace Prize, China's version of the Nobel prize, organisers said.

Putin, who was announced winner of the Chinese prize earlier this year, did not attend Friday's ceremony, so the award was handed over to two Russian exchange students, Qiao Damo, one of the organisers told AFP.

The prize emerged last year, when it was suddenly announced by the academics two days before Liu was awarded the Nobel Peace Prize, sparking speculation it was set up with the government's guidance.

The government has since denied any connection with the prize.