A renowned Chinese human rights lawyer said Beijing airport police blocked him Tuesday from boarding a flight to attend an international legal conference in London.

Mo Shaoping said officers gave only vague reasons for their actions, although it comes amid a new wave of repression against independent activists sparked by the awarding of the Nobel Peace Prize to dissident writer Liu Xiaobo.

Liu's wife and dozens of dissident colleagues have been placed under house arrest or intense monitoring in an apparent attempt to prevent them from attending the Dec. 10 award ceremony in Norway.

Mo, whose firm represents Liu, said he was stopped along with Hong Kong University law professor He Weifang as they were attempting to board a flight for London.

"We were taken to an office by two police and were told that we had been restricted from going abroad because it might harm state security," Mo said. The officers showed their police badges but issued no formal papers, he said.

"It's absurd to stop us with a charge like this and it's a violation of people's basic human rights," Mo said.

Mo said he had no intention of attending the ceremony, but had merely planned to make a previously scheduled presentation on the independence of lawyers at a conference sponsored by the International Bar Association.

"The trip was fixed a few months ago and has nothing to do with the incident of the Nobel Peace Prize. We were supposed to come back on Nov. 15," Mo said.

Unable to leave, Mo said he would file suit against the officers.

Mo has for years been one of mainland China's best known human rights lawyers, but has largely managed to avoid the fate of colleagues who have been disbarred, arrested, or harassed as punishment for their activism.

Many of those have come under even greater pressure following the awarding of the Nobel to Liu last month _ a move met with an indignant response from authorities who have embarked on a full-bore campaign of vilification against Liu and the Nobel committee.

Liu, 54, is serving an 11-year sentence on subversion charges brought after he co-authored a bold call for sweeping changes to the one-party communist political system known as Charter 08. Mo is one of the signatories to the charter.