CHINA yesterday warned Governor Chris Patten to stay out of the case of the arrested Hong Kong reporter, as international pressure mounted for his release. A senior mainland official warned Mr Patten's intervention would only make Ming Pao journalist Xi Yang's case more difficult. ''I hope Mr Patten will not interfere in this matter. It could make the case more complicated,'' said Zhang Junsheng, deputy director of the local branch of Xinhua (the New China News Agency). ''He has so many other things to do. He shouldn't interfere in things like this.'' Mr Zhang's warning came after the Governor expressed concern about the detention and its effect on press freedom as local and international press groups stepped up the campaign for Xi - the second Hong Kong journalist arrested in Beijing in the past year- to be freed. Ming Pao yesterday offered to apologise if it would help win the reporter's release, while the Hong Kong News Executives' Association and International Federation of Journalists expressed concern. But Mr Zhang indicated Beijing was unlikely to bow to pressure. ''This was criminal activity, not related to normal reporting,'' he said. ''The judiciary in Beijing will handle it. They released information when he was detained for investigation. They also released information when they officially arrested him. So you can see it was handled according to the legal procedure.'' He said all journalists travelling in China should have a clear understanding of mainland law. Xi was charged with espionage last Thursday after being arrested a fortnight earlier. It was claimed he had requested a central bank clerk to sell state banking secrets, which were used in a series of exclusive reports in the popular Chinese-language daily. The News Executives' Association yesterday warned China's handling of the case threatened to tarnish its international image, and called for Xi's family and employers to be allowed to visit him. The journalists' federation, representing more than 320,000 journalists worldwide, also said it was deeply disturbed about the case in a letter to Chinese Minister of Justice Xiao Yang Buzhang. Federation general secretary Aidan White said it feared Xi's trial would not be open to the public. It called on the Justice Ministry to release more information about the case, and allow Hong Kong and foreign journalists to attend the trial. Mr White said the federation could not understand Beijing's claim that Xi's actions were ''unrelated to the normal reporting activities'' of a journalist, and warned the federation would continue to monitor the case. In Beijing, Ming Pao executive chief editor Paul Cheung Kin-bor yesterday offered to apologise to Chinese authorities if the reporter was found to have acted improperly. Cheung told the State Security Bureau ''the paper is willing to admit the mistake and apologise on this issue if Xi Yang has done wrong in reporting and we hope the authority could handle it generously''. But Mr Zhang said last night he did not know whether this would help win Xi's release. ''I don't know how the case will be handled. This should be the work of the judiciary in Beijing.'' Cheung said officials told Xi's father his son was healthy and living in good conditions, and promised the newspaper's offer would be conveyed to higher authorities. Cheung said Ming Pao had not contacted the British Embassy in order to avoid politicising the case. British Ambassador to Beijing Sir Robin McLaren said the embassy was doing all it could to arrange for Xi to see his family, and have proper legal representation. Xi, who is in his 30s, was born on the mainland and only came to the territory two years ago. He does not hold a Hong Kong British passport. In Hong Kong, independent legislator Emily Lau Wai-hing attacked Beijing's warning that the Governor should stay out of the case. ''Every Hong Kong person would like Mr Patten to do something for Mr Xi,'' she said, adding she would raise the issue in the Legislative Council. ''I am afraid that nobody will dare write about the Chinese Government anymore.'' Mr Patten said on Friday the Government was closely monitoring Xi's case, but did not want to act in a way which would make his situation more difficult. ''We don't want to do anything which would complicate Mr Xi's case,'' he said. ''I very much hope that, without any controversy, these matters can be dealt with honestly and openly and as quickly as possible because I know they are of grave concern here in Hong Kong. ''There are many Hong Kong journalists who have to go to Beijing and China professionally to do their job who are very concerned because they are not sure what it is that Mr Xi has done wrong.'' But spokesman for the pro-Beijing Democratic Alliance for Betterment of Hong Kong, Lo Chi-keung, yesterday warned Hong Kong and British involvement in the case would be interference in China's internal affairs. ''If we have trust in Chinese law, then we should believe Mr Xi will have a fair trial,'' he said. ''Whether this is open or closed depends on the style of the court because each country has its own system of trials.''