PRESIDENT Jiang Zemin has tried to tighten his grip on power by reining in the activities of his rival, former military strongman Yang Shangkun. Mr Jiang, who chairs the policy-setting Central Military Commission (CMC), has also demonstrated his hold on the People's Liberation Army (PLA) by deploying four army units around the capital on the death of elder Chen Yun on April 10. An army source in Beijing said Mr Jiang had formed a pact with the CMC vice-chairmen, veteran generals Liu Huaqing and Zhang Zhen, against the possible comeback of Mr Yang, a former state president and CMC secretary-general. 'A politely phrased message has been relayed to Yang asking him to refrain from consorting with PLA officers either in Beijing or the regions,' the source said. Since his retirement from state and army positions in late 1992, Mr Yang, 87, who enjoys excellent health, has toured the provinces frequently. In January and February, the former confidant of patriarch Deng Xiaoping was in Guangdong, where he held at least one informal meeting with PLA officers. After getting the message, Mr Yang adopted a low profile. He was absent from a ceremony last week honouring the late marshal Ye Jianying, a close friend. 'Since late 1992, Jiang has masterminded at least three rounds of major reshuffles in the army to get rid of the influence of Yang and his disgraced half-brother, [former chief political commissar] Yang Baibing,' the source said. 'However, Jiang still considers the two Yangs to be his major competitors.' Western diplomats in Beijing said Mr Jiang had also improved relations with Generals Liu and Zhang. Last year, there were reports that Mr Jiang had incurred the ire of the pair by persuading them to retire. It is understood that Mr Jiang has also sought the help of generals Liu and Zhang in containing the influence of retired officers such as generals Zhang Aiping and Qin Jiwei. The diplomats said it was significant that Mr Jiang should use Mr Chen's death to demonstrate his hold over the PLA. By contrast, in the run up to the June 4, 1989 crackdown, a few regional commanders were reluctant to send troops to Beijing in obedience to Mr Deng, then CMC chief. Apart from the death watch over Mr Deng, the political atmosphere in Beijing has been charged with the imminent purge of the municipal leadership. Rumours spread yesterday that Beijing's party secretary Chen Xitong had offered his resignation. Sources in Beijing said that a front-runner to succeed Mr Chen, State Council Secretary-General Luo Gan, had for the moment turned down the hot seat. However, Mr Luo, a confidant of premier Li Peng, has since early this month held special classes for all bureau heads of the Beijing municipality. The classes, to be finished tomorrow , are aimed at 'unifying the thought' of cadres in the face of the recent spate of scandals involving senior officials. Mr Luo told the cadres they must heed Mr Jiang's leadership 'no matter what happens'. He added that the transition to the third-generation leadership with Mr Jiang as its core had been accomplished well.