Chinese security forces blanketed Tiananmen Square on Wednesday ahead of the 20th anniversary of the June 4 crackdown on pro-democracy protesters, a day after Twitter and Hotmail Internet services in China were blocked, Reuters reported.
Black police vans lurked at the side of the Forbidden City, while police and paramilitary forces patrolled through crowds of tourists enjoying a sunny summer morning.
Tanks rolled into Tiananmen Square before dawn on June 4, 1989 to crush weeks of student and worker protests. The ruling Communist Party, which has never released a death toll, fears that any commemoration of the crackdown could challenge its continuing hold on power.
"Business is poor today. You'd think most people are tourists but they aren't, they are plainclothes security," said a trinket peddler surnamed Li, before a plainclothes policeman told her to stop talking to foreigners.
"They are scared there will be a big blow-up because of tomorrow, but I don't think anything will happen."
Chairman Mao Zedong's mausoleum, in the center of the square, was closed for "equipment repairs" from Wednesday through Friday, according to a hastily scrawled handpainted sign.
About 30 people are still serving prison sentences for their activities in 1989, according to the San Francisco-based human rights organization Dui Hua.
Others are in prison for continued activism after their initial release.
Hundreds of other protest leaders are in permanent exile.
In a sign of nervousness, China on Tuesday blocked access to popular Internet services Twitter, online photo sharing service Flickr, and email provider Hotmail. Foreign newscasts about the anniversary were also cut.
Police prevented at least four foreign television crews from filming on Tiananmen Square in the week before the anniversary.
Administrators at Chinese universities have been told to keep a close eye on foreigners in their departments. Taxi drivers were instructed to watch out for suspicious passengers, especially those headed toward Tiananmen Square.
Zeng Jinyan, the wife of imprisoned AIDS activist Hu Jia, was stopped on Wednesday from leaving her home, where she and their baby daughter have been kept under tight surveillance for over a year.