From New York Times:
China blanketed Tiananmen Square with police officers Thursday, determined to prevent any commemoration of the 20th anniversary of a military crackdown on pro-democracy protesters that left hundreds dead.
Visitors to the sprawling plaza in central Beijing were stopped at checkpoints and searched, and foreign television crews and photographers were turned away. Plainclothes police, standing rigidly next to uniformed officers, seemed to outnumber the tourists. White government vans were parked in a line in front of the Mao Zedong’s mausoleum.
Some who wished to remember the bloody end to the student-led movement suggested on Internet chat sites that visitors wear white to the square. But there was no clear sign of that on Thursday morning, nor signs of any other protests.