POLICE in Beijing tightened security around the sensitive college district on the eve of the fourth anniversary of the June 4 massacre, forbidding foreigners to enter the cradle of the 1989 democracy movement. Last night, cars with black licence plates, which are used by foreigners, were not allowed into the Haidian District in the northwest of the city. Police told foreign reporters and diplomats converging on the area that only Chinese with the relevant residence permits would be allowed in. Residents in Haidian said the security was tighter than last year. But police were polite to foreigners and seemed anxious to avoid confrontation. Sources on campuses said about 30 graduate students at Beijing University who were considered by the authorities to be troublemakers were sent home early this week. Security was tight in Beijing yesterday, but overall the mood seemed more relaxed than in previous years. Police in Tiananmen Square seemed relatively tolerant of the presence of foreign journalists. Tiananmen Square, the centre of the pro-democracy rallies, was open to tourists. Under a clear sky and a hot summer sun, hundreds of tourists snapped pictures of each other and ate ice-creams like on any other day. Plain-clothes police were in evidence, and any Chinese seen talking to foreign journalists probably did so at some risk. But it did not seem as if the plain-clothes police were out in the same numbers as last year, when scores of security agents swarmed the square. Police vehicles and military trucks were positioned around the square, but there were fewer uniformed police present than for the previous three anniversaries. Two American television networks went on to the square with cameras, one having obtained permission to do so from the police. They were told that they could film, but not talk to anyone, according to a foreign television journalist. After 20 to 30 minutes, the camera crews were told to leave. On previous anniversaries, police often scuffled with journalists, breaking their cameras and taking some correspondents away for questioning. At the far western end of Changan Avenue, the capital's main east-west artery, a small businessman said police had recently ordered him and others away from a place where they had previously plied their trade. Apparently the police wanted the area, whereseveral hotels are located, cleared for the anniversary. Police ordered the businessman to leave for 10 days, until June 8. ''They didn't say why, but I know it's because of June 4,'' the man said. ''People have not forgotten June 4,'' he added. Another man at the same street corner said ordinary Chinese were more concerned at the moment about inflation than the anniversary. ''People are worried about prices. Money isn't worth anything,'' he said. As in the run-up to the tumult of 1989, China is again facing spiralling inflation, which is running at 17 per cent a year in the country's major cities. And, as before 1989, corruption is again rife. But the man said the problem was not with the Communist Party leadership. ''The policies above are good, but they aren't carried out,'' he said.