The appointments and the detentions reflect the academy's higher profile as well as the risks that prominence brings.

Professor Xia's promotion last month should not have come as a surprise to CASS scholars because the academy has become a reserve of talent for the central government. Many CASS scholars have been seconded or promoted to officialdom, and sources say the past few months alone have seen several examples.

Zhang Ximing, deputy director of CASS' Institute of News and Media Study, was appointed deputy director of the powerful Theoretic Bureau of the Communist Party's publicity department. The bureau oversees the country's ideological and theoretical study and directs the state media's propaganda work.

Jiang Xiaojuan , director of CASS' Institute of Finance and Trade Economics, was named a deputy head of the State Council's Research Office. The research office's main function is to prepare reports and speeches for the premier and his deputies. It also conducts investigations assigned by state leaders.

A leading legal expert who helped draft Hong Kong's Basic Law, Professor Xia has had little to do with state secrecy.

He is known in Hong Kong as one of four mainland 'guardians' of the Basic Law for his argument that Beijing has the final say on the special administrative region's constitutional-reform issues.

Professor Xia has been to Hong Kong several times in the past two years for forums and seminars and he has often said that as an academic he did not represent the central government. But his public comments are believed to reflect official thinking. 'Very often, their visits have been arranged to informally articulate Beijing's position ahead of a major decision on SAR affairs made by the central government,' an insider said.

A CASS American-affairs expert told the South China Morning Post Professor Xia had also been to the United States several times to meet academics, US State Department officials and congressmen to solicit opinions on key issues on behalf of the central government.

Insiders say Professor Xia has also headed an investigative office under the general office of the decision-making Communist Party Central Committee. The office is often assigned by top party leaders to conduct investigative missions. Professor Xia's experience was apparently a contributing factor to his new appointment.

It has been widely reported that Professor Lu had also undertaken such missions in his past visits to Hong Kong. Many CASS scholars have been assigned such jobs, the CASS American-affairs expert said.

Many CASS scholars have also been giving senior government figures the direct benefit of their expertise in the past two years by delivering lectures to state leaders.

Behind the vermillion walls of Zhongnanhai, Pei Changhong , director of CASS' Institute of Finance and Trade Economics, and Huang Weiping of Renmin University had held face-to-face talks with President Hu Jintao , Premier Wen Jiabao and other senior leaders.

Since the first such presentation in December 2002, the Politburo has held 22 study sessions and summoned more than a dozen prominent CASS scholars to give briefings to top leaders.

CASS economist Yi Xianrong said the top leadership was increasingly seeking advice from the academy because, as an independent think-tank, CASS could be objective and balanced.

'Ministries, central agencies and local governments have vested interests on policy issues and often produced biased reports,' Professor Yi said.

Professor Yi's recent controversial reports claiming that the mainland property market could crash - just as it did in Hong Kong after the Asian financial crisis - have drawn fierce criticism from various interest groups such as developers and even officials from the Ministry of Construction.

CASS' reports on the widening income gap apparently prompted the leadership to focus on the poverty issue.

The reports also played a role in President Hu's emphasis on building a 'harmonious society' since September.

'The new leadership and ministers are better trained and more professional, thus they are more willing to listen to different opinions from the academics,' Professor Yi said.

Professor Lu once played a similar role to Professor Xia in Hong Kong affairs, reportedly visiting the city to solicit opinions from local leaders on behalf of the central leadership.

But his role did not exclude him from surveillance by the state secret police who keep an eye on officials and scholars. And now protecting state secrets is Professor Xia's new job.