Costly date: 64.89 yuan forbidden on Tiananmen June 4 anniversary

China's information blackout about the crackdown on the 1989 Tiananmen protests took a new turn today: users of a popular social media app could not send each other money transfers alluding to the anniversary date.

Open discussion of the brutal crackdown is forbidden in China, where hundreds -- by some estimates more than a thousand -- died when the Communist Party sent tanks on June 4, 1989 to crush a student-led demonstration calling for democratic reforms. The United States called on China on Monday to disclose how many were killed, drawing a rebuke from Beijing, which brands the protest as a "counter-revolutionary rebellion".

Foreign news broadcasts on commemoration events are usually blocked while survivors and the families of those killed are put under surveillance or forced to travel out of Beijing as the anniversary approaches. Security prevented an AFP photographer from approaching the square today.

Social media is also heavily controlled, and on Monday users of the ubiquitous WeChat application were unable to exchange "red envelopes", or money packets, valued at 89.64 yuan or 64.89 yuan, indicating the date of the anniversary.

A "system busy. Try again later" message appeared every time AFP journalists tried to complete a transaction involving the sum, but the service functioned smoothly if the amount was changed, suggesting deliberate censorship.

People in China use clever tactics to circumvent censorship. When dissident Nobel laureate Liu Xiaobo died of cancer while in custody last year, people posted candle emojis as a discreet tribute. Those wanting to allude to the #MeToo movement have used emojis and the Chinese characters for rice and bunny, which are "mi" and "tu".

Chinese search engine Baidu did not yield any results for the term "29th anniversary of Tiananmen massacre" during the past week and posts on any commemoration events were missing from China's Twitter-like microblogging platform Weibo.

The Chinese government has "spent enormous amounts of resources" to enforce a "thorough and all-encompassing" erasure of information linked to the incident, William Nee, a China researcher at Amnesty International Hong Kong, told AFP.

"This year, it might be incrementally more effective, since the government has increased self-censorship on WeChat groups and has become better at using artificial intelligence to proactively ban what it deems to be problematic photos." Tencent Holdings, which operates WeChat, could not be reached for comment.

Several prominent bloggers and activists were forced to go on "vacation" under police escort ahead of the sensitive date.

Dissident democracy activist He Depu told AFP that two policemen drove him to a hotel in the Yellow Mountains, a popular tourist resort in central China, on May 31, and he will only be allowed to "checkout" on Tuesday afternoon. Activist Hu Jia said two national guards drove him from Beijing to a hotel in the centre of Qinhuangdao, a beach resort about 300 kilometres (180 miles) east of the capital on June 1.

"This is already my 14th year of being forced to take a vacation on June 4. But, wherever I am, I fast the whole day and light candles to commemorate the struggle," he said.

"After all, I feel lucky... to be a survivor. On this day 29 years ago, the bullets flew over my head. I also feel saddened... because so many people died, but China is still stuck in 1984 in terms of (political) progress." - US demands death toll -