There are only two places under Beijing's control where commemoration of the events of Tiananmen Square are tolerated by the authorities - Hong Kong and the former Portuguese enclave of Macau.
By Chris Hogg
BBC correspondent in Hong Kong
From September, school children in Hong Kong will also have the opportunity to read about the killings of 15 years ago.
Four pages on the Tiananmen protests are to be included in a new textbook, following a decision to add them to the territory's new Chinese history syllabus.
The teacher who wrote the section, Wong Chi-man, admitted he had taken a cautious approach.
Wong Chi-man admits to caution over his portrayal of the protests
"I've stuck to the facts," he said. "I've just tried my best to write what needed to be written."
The language is neutral. The text describes how the square was "cleared" at the end of the protest.
There is no description of the tanks that were used against the protestors, or of the bloodbath that followed.
Mr Wong said he had to leave out such details to ensure that the editors of the textbook did not reject his chapter.
He said he thought it was more important to ensure the event was included in the textbook at all.
"It is very important in Chinese history," he said. "These were students who lost their lives because they fought for freedom and democracy. It is worthy to commemorate this event and let the [Hong Kong school] students learn from history."
The organisers of events in Hong Kong to commemorate the 15th anniversary of the Tiananmen Square massacre said they were expecting record numbers of people to take part this year.
They claimed that, at least in part, this was due to recent political events in the territory.
A few weeks ago Beijing's parliament, the National People's Congress, ruled that universal suffrage would not be introduced in Hong Kong in time to elect the territory's leader in 2007.
1989 TIANANMEN EVENTS
15 April - Reformist leader Hu Yaobang dies
22 April - Hu's memorial service, thousands call for faster reforms
13 May - Students begin hunger strike as power struggle grips Communist party
15 May - Soviet leader Mikhail Gorbachev visits China
19 May - Zhao Ziyang makes tearful appeal to students to leave
20 May - Martial law declared in Beijing
3-4 June - Security forces clear the square, killing hundreds
The announcement was followed by the resignation of three controversial radio hosts, who complained they were subjected to threats and intimidation by "pro-Beijing forces".
None of the three have produced any hard evidence to back up their claims, but there are increasing fears that free speech is under threat in the former British colony, in the run-up to the elections for Hong Kong's mini-parliament in September.
"Recently there are many signs that they want to reduce free speech here," said the Roman Catholic Bishop of Hong Kong Joseph Zen.
"We must wake up and defend this freedom, which is very fundamental, because without this freedom Hong Kong would be hopeless," he said.
The outspoken primate said he backed protests to press for more democracy, both in Hong Kong and China.
He described himself as "optimistic" that the Chinese leadership would eventually change its position on the protests in Beijing 15 years ago.
"You can talk more openly about Tiananmen Square these days," he said. "I hope a reversal of their position won't be so far away."
'Dirty tricks' allegations
Pro-China politicians in Hong Kong like Ma Lik, the chairman of the Democratic Alliance for the Betterment of Hong Kong, find themselves forced to defend their allies in Beijing against allegations they are running a dirty tricks campaign in the territory.
"I don't think the central government officials are that dirty to try to fight the people, or to try to stop them criticising the government," he said. "It would backfire on them."
Ma Lik is concerned that pro-democracy politicians in Hong Kong are using the row over the alleged threats to radio hosts to try to drum up anti-Beijing sentiment.
"They will tell voters, if you want to send a message to Beijing, don't vote for my party," he complained.
"We will be squeezed, making it easier for them to win more seats in the Legislative Council."
But Hong Kong lawmaker Lee Cheuk Yan rejected that idea.
He was involved in the struggle in Beijing 15 years ago, and was detained after attempting to deliver funds collected in Hong Kong to the students in Tiananmen Square.
Now he is at the forefront of efforts to commemorate the events of 4 June 1989, and to try to force the authorities to introduce what he calls "full democracy" in Hong Kong.
"In the past we felt we had to push to try to achieve democracy in China," he said.
"Now we feel we have to defend Hong Kong against the regressive hand of Beijing."
"Fifteen years after Tiananmen Square, we are now feeling the same pressure from Beijing that the students felt. We have to use what freedoms we have to defend ourselves."