Relatives of Chinese citizens shot dead during the 1989 Tiananmen Square massacre have defied unprecedented Communist Party attempts to silence them and are demanding the truth about their loved ones’ deaths ahead of Wednesday’s 25th anniversary of the uprising. More than 150,000 people are expected to gather at a candlelit vigil in Hong Kong’s Victoria Park on Wednesday night to commemorate the still unknown number of lives lost during Beijing’s offensive against pro-democracy protesters that reached its peak on June 4, 1989.

But in mainland China, where activists accuse the government of waging a vindictive campaign of intimidation in the lead-up to the anniversary, public commemoration of the event remains strictly forbidden. At least 50 people have been “detained, disappeared or summoned for police questioning” since April, according to figures compiled by the Chinese Human Rights Defenders (CHRD) group. They include writers, activists, artists, lawyers, journalists and filmmakers, as well as the elderly relatives of those killed in 1989. Among those placed under house arrest is Ding Zilin, a university professor who founded the campaigning group Tiananmen Mothers after losing Jiang Jielian, her 17-year-old son. Renee Xia, CHRD ‘s international director, said this year’s oppression by the government appeared to have been the toughest since Tiananmen.

“The leaders are more nervous because they feel less secure due to increasing social conflict and widespread discontent. They fear any display of dissent might spark protests against the government,” she said.

A number of families have chosen to defy Beijing’s attempts to muzzle them.

“All I want now – all I have ever wanted – is for the truth to be published,” said Ma Xueqin, whose 19-year-old daughter, Zhang Jin, was hit in the head by a stray bullet as she left work on the eve of the massacre.

“They dare not tell the truth because the truth is too cruel. So much killing.”

Liu Meihua, who lost Xie Jingsuo, her 21-year-old son, said: “My only wish is for the government to re-evaluate the June 4 incident. I have felt sad every single day since my son’s departure.

“No government body has ever offered us an explanation or a solution or taken responsibility for the issue. Young people today know little about June 4, since it is rarely read about or talked about, and the older people are dying out.”

To this day, Beijing’s official line is that the decision to send thousands of troops to clear Tiananmen Square on the night of June 3 was a “prompt and decisive” reaction to a “counter-revolutionary riot.” No public inquiry has ever been held and those who lost relatives still have no clear idea about the exact circumstances in which their loved ones were slain.

Speaking on the eve of the anniversary, Salil Shetty, Amnesty International’s secretary general, called for an “open and independent inquiry” into the killings and condemned Beijing for seeking “to wipe the events of June 4 from memory.” “These devastated families deserve a full and open account from their government,” he added.

Ma, 69, said that her daughter had died after being hit by a stray bullet at around midnight on June 4, 1989. “The soldiers were firing at random in every direction,” she said. “What did my girl do to deserve this?” Ma said that warnings and threats from the security services would not silence her. “I have done nothing wrong. It has been so many years. I have nothing to fear. They can never erase history.”

Sharon Hom, the executive director of the Human Rights in China campaign group, said that after 25 years of trying to bully such families into silence, Beijing’s tactics were no longer working.

“The surveillance, the threats, the monitoring, the phones, all of that: They have kind of reached a plateau,” said Hom. “Fear is no longer effective to keep them silent. Now they are going to speak out.”