Tuesday marks the 35th anniversary of China's deadly crackdown on pro-democracy protesters at Tiananmen Square in Beijing.

Authorities have tightened control under the leadership of President Xi Jinping. They have thoroughly suppressed calls from bereaved families to find the truth about the incident.

On June 4, 1989, Chinese troops opened fire on students and others who had gathered in and around the square to demand democracy. The Chinese government says 319 people died, but some people say the figure is much higher.

A group of victims' relatives called the "Tiananmen Mothers" in May posted a statement signed by 114 people on its website.

The message called on the government to make public the number of victims and their names, compensate the victims and their families, and pursue legal responsibility for the incident.

The Chinese public cannot read the online statement as its access is restricted in the country.

Publicly discussing the incident is regarded as taboo in China. The government maintains that the incident was "turmoil" and it made the right decision.

The relatives' group initially planned to hold a memorial service to mark the 35th anniversary at a member's home. But they say they had to give up the plan due to strict monitoring by authorities.