In China, the Tiananmen Square massacre is a pretty sensitive topic to discuss. That is why; the nation speedily censors Web content which is even faintly serious of the event.

That was positively still the case on Friday, when the 21st anniversary of the event took place, and China blocked that location-based social network, Foursquare, after users started logging in at Tiananmen Square on the service.

Under Foursquare's process of checking in, users can tell followers where, physically, they are. The information can be syndicated to Facebook or Twitter. People who are checked in at the same location can engage in conversation.

According to an account in Techblog86, a China-based site that initially broke the news of China's choice to block Foursquare, people, who checked in to Tiananmen Square were leaving sensitive remarks on the page so that others could see it as well.

Those comments were publicized and shared with friends and followers on Facebook and Twitter. China, whilst objecting to such commentaries made a decision to block the service in an effort to suppress the protest.

China has yet to verify that it has actually blocked the site or not. The Company as well did not immediately respond to request for comment.