For some years now, the discussion of the 1989 clampdown when the Chinese government set tanks and troops on peaceful protestors is all but forbidden in mainland China.

Tiananmen Square Massacre: What really happened in 1989?

Searches for the famous Tiananmen Square 'Tank Man' protest photo came up empty on Microsoft search engine Bing on Friday, raising censorship concerns on the anniversary of the deadly crackdown.

Famed 'Tank Man' photo vanishes from Bing search engine

Hong Kong police detained prominent democracy activist Chow Hang-tung on Friday morning, with authorities determined to prevent any protests on the anniversary of Beijing's deadly Tiananmen crackdown.

Hong Kong police detain democracy leader on Tiananmen anniversary