A Beijing citizen standing in front of tanks on the Avenue of Eternal Peace in June 1989, during the crushing of the Tiananmen Square uprising. Photo: Stringer/Reuters

Twenty-five years ago, Wang Nan took his camera and headed out to Beijing’s Tiananmen Square, where tens of thousands of people had gathered calling for democratic reforms. The 19-year-old told a friend he wanted to record history.

Before he left his home late on June 3, 1989, he asked his mother:”Do you think the troops would open fire?” She said she did not. Around three hours later, he was shot dead by soldiers.

As his 77-year-old mother, Zhang Xianling, prepared to mark the 25th anniversary of her son’s death, she was under around-the-clock surveillance by eight police and security officers.

Zhang said the level of scrutiny this year was unprecedented. As early as April, police officers barred foreign journalists, including Reuters reporters, from visiting her home. “I find it ridiculous, I’m an old lady,” Zhang told Reuters by telephone. “What can I say [to reporters]?

“I don’t know any state secrets. All I can talk about is the matter concerning my son. What is there to be afraid of?”

The Chinese Communist Party’s harshest crackdown on political dissent in recent years would suggest plenty. For Zhang, whenever she wants to travel anywhere she is driven in a police car. Two police officers walk with her when she goes to the market.

In previous years, Zhang said she was usually guarded by three to five police officers who would appear outside her home a month before the anniversary. The extraordinary measures are explained by the fact that she is one of the co-founders of a group of families called the Tiananmen Mothers, who have long demanded justice for the victims of the massacre.

Ding Zilin, the other co-founder who was travelling in the eastern city of Wuxi, near Shanghai, was not allowed to return to Beijing, said Zhang and other rights activists.

“There is much empathy for them given they lost children in 1989,” said William Nee, Amnesty International’s China researcher. “They are seen as credible and their continued fight for justice, especially given their age, has drawn much sympathy. The authorities are acutely aware of this and that is why we believe they are placed under such heavy surveillance this year.”

Asked about the restrictions on the Tiananmen Mothers, China’s Foreign Ministry spokesman Hong Lei said the legal rights of Chinese citizens are guaranteed, but every Chinese citizen must “consciously respect the country’s rules and laws”.

Since Xi Jinping became President in March last year, his administration has taken a hard line on dissent, detaining and jailing activists, clamping down on internet critics and tightening curbs on journalists in what rights groups call the worst suppression of free expression for several years.

“The government is concerned about what they call stability maintenance,” said Andrew Nathan, a professor of political science who specialises in Chinese politics at Columbia University in New York. Nathan said Chinese leaders are concerned about the so-called ‘Arab Spring’ uprisings and revolutions in Ukraine, and want to prevent such open acts of rebellion against the state from taking hold in China.