Three decades ago, tens of thousands of Chinese people demonstrated in Beijing for democracy and freedom.
It was the biggest threat to the ruling Communist Party since it came to power in 1949.
The government responded to the mainly student-led protests by declaring martial law and then ordered tanks and armed troops to Tiananmen Square at the heart of the capital and carnage ensued.
Because the repression was highly-censored by China, there are no official statistics on the number of people killed on June 3-4, 1989. Activists and rights groups have estimated it to range from hundreds to thousands.
Security in Beijing was tight for the anniversary, and any public discussion can result in imprisonment.
Sympathisers have been holding vigils in Hong Kong and Macau, two semi-autonomous Chinese territories where freedom of expression is allowed.
How have the killings in Beijing shaped modern China?
Presenter: Halla Mohieddeen
Claudia Mo – Hong Kong legislator and pro-democracy activist
Nury Turkel – American lawyer of Uighur heritage
Andreas Fulda – Author of The Struggle for Democracy in Mainland China, Taiwan and Hong Kong