China, which has long been criticized for its human rights record, has cracked down on dissent to stave off potential political instability, the human rights group said.

"The government seems afraid that its own citizens will embarrass it by speaking out about political and social problems, but China's leaders apparently don't realize authoritarian crackdowns are even more embarrassing," Brad Adams, the Asia director of New York-based Human Rights Watch, said in a statement.

The Beijing Olympics, which begin Aug. 8, 2008, are a huge source of pride for China. In bidding for the games back in 2001, Chinese leaders promised International Olympic Committee members that the Olympics would lead to an improved climate for human rights and media freedoms.

Instead, there has been "gagging of dissidents, a crackdown on activists and attempts to block independent media coverage," Adams said.

The Chinese Foreign Ministry had no immediate comment on the Human Rights Watch statement. In the past, China has said it was fulfilling all the commitments made in it's bid for the games.

The IOC said it believed the Olympics have had a positive effect China.

"While some may question China's ability to meet it's obligations related to the Beijing Games, we think it is premature to state that China has failed to live up to it's pledges," IOC spokeswoman Giselle Davis said.

Human Rights Watch sighted several examples of activists who have been obstructed, including a husband-and-wife couple, Hu Jia and Zeng Jinyan, who have been under constant surveillance and travel restrictions since May for allegedly "harming state security."

Others include Jingo Yanking, a military surgeon who broke government secrecy to reveal the true scale of Beijing's SARS outbreak in 2003. He has reportedly been banned from leaving China to accept a human rights award in New York.

Hu, an AIDS activist, said law enforcement authorities told him last year, while he was in custody for nearly six weeks, that Olympic security measures started two years ahead of the Beijing Games.

"Olympic security includes extinguishing all threats," he said. "The greatest threats aren't necessarily terrorists or crime, the greatest threats are those who reveal China's social problems and protest the government."

Like many dissidents, Hu is under constant surveillance by plainclothes officers. His wife, Zeng, who is five months pregnant, was barred from attending a human rights meeting in Switzerland in June and had her passport confiscated.

For foreign journalists in China, Beijing has loosened decades-old reporting rules that required government approval for travel and interviews. Yet at the same time, it has clamped down on domestic media and Internet essayists.

"The Chinese government shouldn't waste this unique opportunity to use the 2008 Games to demonstrate to the world it is serious about improving the rights situation," Adams said.

The group also criticized Beijing's ties with oppressive regimes and dictatorships in Sudan, Burma, Cambodia and Zimbabwe. China has been accused of not doing more to stop the bloodshed in Darfur, where more than 200,000 people have been killed and 2.5 million others displaced since February 2003.

China buys two-thirds of Sudan's oil exports, exports weapons to the country and is an investor in Sudanese dams and other infrastructure projects. Beijing has urged a political solution to the Darfur crisis and, as a veto-wielding member of the U.N. Security Council, has blocked efforts to sanction Khartoum.

Steven Spielberg, who is working as a consultant on the Games' opening ceremony, has urged Chinese President Hu Jintao to change his government's policy on Sudan after the filmmaker was publicly branded a collaborator by Mia Farrow.

Farrow, a U.N. goodwill ambassador, has labeled the Games the "genocide Olympics."