China's move to once again block Internet sites that had been accessible for several months, comes as activists report a growing crackdown on dissent in the country.
For Internet users in China, a message saying the website they are searching for cannot be displayed is showing up with frequency.
The blocked sites include the Voice of America, in English and Chinese, the human rights organization Amnesty International and the Taiwanese and Hong Kong versions of the video-sharing website YouTube.
On August 1, the Chinese government bowed to international pressure to stop blocking the sites, as a prelude to China's hosting the Olympics.
As of Monday, the controls were firmly back on.
Rebecca Mackinnon is an assistant professor in new media at Hong Kong University's journalism school and a former Beijing Bureau chief for CNN.
She says the Chinese government's actions are consistent with how it deals with what she describes as a "troubled period."
"It would make sense, logically, that given that we're approaching the 20th anniversary of the June 4 crackdown, and given that there are a number of other anniversaries coming up this year, and given that we also have a global financial crisis, and China's economy is facing a tough patch, it would be very consistent with regime's past behavior to tighten up on things like the Internet, on the media, and other kind of forms of expression that might help to fuel discontent or might help enable people to organize or anything like that," she said.
The June 4 crackdown is better known as the Tiananmen Square crackdown. On June 4, 1989, Chinese troops opened fire on and killed hundreds of pro-democracy activists who had been demonstrating on Tiananmen Square.
The tightening of Internet controls comes less a week after dissidents issues a prominent manifesto, called "Charter '08," that calls for legal reforms and greater democracy.
Mackinnon says it is hard to tell whether the latest Chinese government move to block international websites is related to Charter '08, or whether it is something that just happened to coincide.
She notes that, any times in China, some things will get tighter while other things will become looser.
"People I know who are journalists in China say that they have less freedom to do investigative reporting now than they had ten years ago. Whereas people on the Internet feel that, while they're censored and so on, and there's a lot of problems, they still have a much greater space in which to talk about a variety of things, than they have had anywhere else in China, at any other time," said Mackinnon.
In defending the Chinese government's move, Foreign Ministry spokesman Liu Jianchao says China manages the Internet according to law.
Liu says some websites violate Chinese law, such as websites that advocate what he calls "two China's" - which would be mainland China and an independent Taiwan.
He did not cite any specific cases, but he urged websites not to do things that violate Chinese law.
Despite a loosening on many websites right before the Olympics, sites that have always remained blocked included those that dealt with the outlawed group, Falun Gong, and other sensitive topics, such as Tibet.
