China has reportedly detained or threatened dozens of people as part of a "wave of persecution" targeting those seeking to commemorate the victims of the Tiananmen Square massacre.
Tuesday will be the 30th anniversary of the infamous crackdown, which saw the Chinese army kill hundreds, possibly thousands, of protesters taking part in student-led pro-democracy demonstrations in Beijing's central square.
Discussion or even acknowledgement of the 1989 incident has for years been suppressed by Chinese authorities in an attempt to erase collective memory of the bloodshed.
Amnesty International accused Xi Jinping, the Chinese president, of using the "same tired political playbook" in "cruelly persecuting those seeking the truth about the tragedy".
"The Chinese government must accept that no amount of suppression will ever erase the horror of the wholesale slaughter that took place in and around Tiananmen Square," said Roseann Rife, East Asia research director of the charity.
Chinese Human Rights Defenders (CHRD), a US-based group supporting activism in China, said a number of activists had been taken into custody to "silence any expression or thwart any action" this year.
The group said it had documented cases involving 13 people who had been detained or "forced into disappearance", including dissident writer Shen Liangqing, who was allegedly seized while walking his dog on charges of "picking quarrels". CHRD said Mr Shen was denied food, water and the use of a toilet for 24 hours.
Last Tuesday, six artists from Beijing went missing while on a "national conscience" tour, according to the wife of one of the men, Zhui Hun. He was also detained for "picking quarrels" and police confiscated his artwork, his wife said.
Authorities also reportedly put three activists on "forced travel" to prevent them from taking part in any demonstrations or from speaking out. One activist, Ou Biaofeng, has allegedly been removed to Guizhou and Yunnan provinces for at least two weeks, accompanied by security officers.
Human Rights Watch said a number of "Tiananmen mothers" - women whose children were killed in the crackdown - had been restricted from travelling or placed under house arrest.
Wang Yaqiu, a China researcher at Human Rights Watch, said authorities still refuse to recognise the atrocities 30 years ago and had failed to compensate victims and their families.
"Concealing the truth and strengthening the rule of high pressure throughout the country will only inspire the determination of human rights activists to pursue human rights and justice," she said.
In a statement, Amnesty International said: "The Chinese authorities must end a wave of persecution targeting those seeking to commemorate the victims of the 1989 Tiananmen crackdown."