Two prominent legal scholars and rights advocates bound for an international law conference in London were blocked from leaving China on Tuesday on vague charges that their departure might endanger national security, they said. The scholars, Mo Shaoping and He Weifang, said they suspected that the government feared that they would try to attend the Nobel Peace Prize ceremony in Oslo next month honoring jailed dissident Liu Xiaobo. Both men were on the list of 143 Chinese activists, academics and celebrities that Liu's wife invited to the award ceremony in an Internet posting two weeks ago, noting that neither she nor her husband were likely to be allowed to attend. Mo and He said that officers who detained them said a superior had described their overseas journey as a threat to state security. 'That's the most imbecilic thing I've heard,' Mo said in an interview, adding that he had no intention to travel to Oslo. 'I don't have a visa for Norway, and I have a ticket to return to Beijing on Nov. 15.' In recent weeks, the government has demonstrated its resolve to stop Chinese citizens from attending the ceremony Dec. 10. It has kept Liu's wife, Liu Xia, incommunicado in her Beijing apartment and subjected scores of other writers, academics and lawyers to varying degrees of detention or surveillance. Among those facing restrictions are Hua Ze, a Beijing-based filmmaker who was forcibly returned to her hometown in southern China; Liu Suli, a Beijing bookstore owner who says he was injured during an assault by security agents last month; and Yu Fangqiang, a human rights lawyer who was stopped at the Hong Kong border last Friday on his way to a United Nations training session in Geneva. At the same time, China has ramped up pressure on foreign governments, warning foreign officials to stay away from the event next month or 'bear the consequences,' as Cui Tiankai, China's vice foreign minister, put it last week. On Tuesday, the Japanese foreign minister told Parliament that Beijing had requested Japan not to send a representative to the ceremony. Liu, 54, an essayist who is among China's best known advocates of political reform, is serving an 11-year prison term for his writings, including Charter 08, a manifesto calling for improved human rights, the rule of law and an end to single-party rule. In addition to using its newfound economic might to warn world leaders away from the ceremony, China has waged an equally vociferous campaign at home to tarnish Liu's reputation and delegitimize the award in the eyes of the Chinese people. After a brief news blackout on the announcement of the prize, the country's state-controlled media began rolling out articles and editorials describing the award as an insult to the country's criminal justice system, a ploy to hold back China's rise and a tactic to subvert the country's political system. Other commentaries have painted Liu as a corrupt pawn of Western governments. The warnings have already prompted a handful of European countries, among them France, Britain, Austria, Sweden and the Netherlands, to announce that they would hew to established protocol and send ambassadors. Michael C. Davis, a law professor and human rights expert at the Chinese University of Hong Kong, said he thought that China's effort to organize a boycott of the ceremony -- like its earlier campaign to dissuade the Norwegian Nobel Committee from selecting Liu -- would probably backfire. In fact, he said Beijing's overall handling of the matter was only drawing more attention to Liu's plight and to the country's checkered human rights record. 'The Chinese often unintentionally turn their enemies into heroes,' he said. Mo, an outspoken advocate of legal reform who signed the Charter 08 manifesto, has so far escaped serious persecution. He was barred from defending Liu last year, but other lawyers from his firm were allowed to take on the case. He, a prominent legal scholar at Peking University, has made frequent critiques of China's judicial system, which may have played a role in his recent transfer to an isolated university in western China. Both men were scheduled to take part in discussions in London on Wednesday about the difficulties facing civil society lawyers in China. Speaking at a restaurant in Beijing, where they were fielding media calls, the two said the decision to block them from the conference was nonsensical. 'This is the Chinese government defacing its own image on the international stage,' He said. 