Chinese authorities have banned online discussion and searches linked to the June 4, 1989 military crackdown in Beijing, as the country's state security police stepped up pressure on activists ahead of next week's sensitive anniversary.
Keyword searches in Chinese for "24th anniversary" and "demonstration" were blocked on the popular microblogging site Sina Weibo from May 25, according to the China Digital Times, which monitors online and mainstream media censorship.
The names of three activists from the southern city of Guangzhou who were detained by police after seeking approval for a demonstration to commemorate those who died in the massacre, were also banned on the Twitter-like service, it said.
Hubei-based activist Liu Feiyue, who runs the People's Livelihood Watch website, said he had been contacted in recent days by state security police from his hometown of Suizhou, and warned not to post articles linked to the anniversary.
"The state security police paid a call on me twice [on Monday]," Liu said on Tuesday. "They told me that I wasn't to report anything linked to June 4 or post anything with figures or content on that topic."
"They made a lot of demands, and it goes without saying that I'm not allowed to leave my home," he added.
"Today, they came again and said there was an article on our website that had to do with June 4...and that I would have to take it down," Liu said.
"So I guess we're in the sensitive period for June 4, and that means a whole raft of stability maintenance measures linked to the June 4 anniversary."
Sichuan-based rights activist Huang Qi, whose Tianwang rights website was originally set up to support the families of victims of the 1989 crackdown, said he had been under surveillance by local police since Sunday.
"Nobody wants our Tianwang website to keep putting out articles during this sensitive time around June 4, and they have made this clear by contacting us via some well-meaning friends," Huang said.
He said his website has now been running for 15 years and has never succumbed to official pressure in all that time.
"We have never stopped for a single day, so we will continue to support people in their attempt to defend their rights, all through the June 4 period," Huang said.
Meanwhile, veteran Hangzhou-based democracy activist Chen Shuqing said he was also under surveillance.
"I think they're afraid I'll go out and take part in some kind of activity," Chen said. "I [and fellow activists] Lu Gengsong and Zou Wei will be under surveillance for sure."
Call for reappraisal
Activists and the relatives of victims of the June 4 crackdown have stepped up pressure on the Chinese government in recent years for an official reappraisal of the 1989 military crackdown on unarmed pro-democracy protesters in Beijing's Tiananmen Square.
Beijing's censors typically muzzle any online or media discussion of the topic, rolling out annual security measures and surveillance targeting political activists and the families of victims.
Beijing-based Zhang Xianling, a member of the Tiananmen Mothers group for relatives of those who died or were injured in the crackdown, said she and her husband had been prevented from traveling to Hong Kong in early June, even though their return flights would bring them back to China by June 1.
"I think they are very afraid right now...they have been for a long time," said Zhang, whose 18-year-old son Wang Nan died during the 1989 bloodshed.
"That's why they won't let us leave."
Hong Kong demonstrations
Last year, tens of thousands of people converged on Hong Kong's Victoria Park to mark the 23rd anniversary, in what has become something of a political tradition in the territory.
Under the terms of its 1997 handover from British rule, Hong Kong has been promised the continuation of existing freedoms of expression and association for 50 years, although the territory has blocked former Tiananmen student leaders from entering the city to attend previous anniversary events.
Retired university professor Ding Zilin, who founded the pressure group Tiananmen Mothers after her 17-year-old son died in the bloodshed, said this week that the annual Hong Kong demonstrations were a source of great comfort to her.
The number of people killed when People's Liberation Army (PLA) tanks and troops entered Beijing on the night of June 3-4, 1989 remains a mystery.
Beijing authorities once put the death toll at "nearly 300," but the central government, which labelled the six weeks of unarmed pro-democracy protests and hunger strikes a “counterrevolutionary uprising,” has not issued an official toll or name list.
Reported by Qiao Long for RFA's Mandarin Service, and by Liu Yun for the Cantonese Service. Translated and written in English by Luisetta Mudie.