Sites linked to the banned Falungong spiritual movement and other unspecified ones would remain blocked for the thousands of foreign reporters covering the Games, organising committee spokesman Sun Weide told AFP.
"During the Olympic Games we will provide sufficient access to the Internet for reporters," said Sun Weide, spokesman for the organising committee.
However "sufficient" access falls short of the complete Internet freedoms for foreign reporters that China's communist authorities had promised in the run-up to the Games, which begin on August 8.
The head of the International Olympic Committee's press commission, Kevan Gosper, told AFP that he would take the matter up with Chinese authorities.
"I have heard that there are some limitations on access," said Gosper.
"I will speak with the Chinese authorities to advise them of the restraints and to see what their reaction is."
Australian Olympic team chief John Coates, who is also an IOC member, expressed frustration with the decision to continue to censor the Internet, pointing out that China had gone back on one of its "key" Olympic promises.
"It certainly is disappointing... I think it's a matter that the IOC will take seriously," Coates told reporters at the main press centre for the Games here where sensitive Internet sites remained blocked.
Coates said that IOC president Jacques Rogge and Gosper would have "very serious discussions with the Chinese authorities" about the issue.
However he said he was not sure whether the IOC had the power or influence to convince the authorities to give foreign reporters free access to the Internet.
"What (IOC leaders) can do about it, I don't know," he said.
In an exclusive interview with AFP two weeks ago, Rogge insisted that there would be no censorship of the Internet.
"For the first time, foreign media will be able to report freely and publish their work freely in China," he said.
"There will be no censorship on the Internet."
However Sun said China's pledge was only to allow foreign reporters enough information to carry out their duties, not to have unfettered Internet access.
"Our promise was that journalists would be able to use the Internet for their work during the Olympic Games," he said. "So we have given them sufficient access to do that."
Falungong is a particularly sensitive issue for China's communist authorities, who outlawed the group in 1999, describing it as an evil cult.
Thousands of their practitioners staged a protest in central Beijing after the group was outlawed, and Falungong members in China report they continue to face severe repression.
Sun would not say which other sites would remain censored for foreign reporters.
But journalists working at the main press centre for the Olympics reported they could not access sites belonging to rights group Amnesty International and a range of media outlets such as the BBC and Germany's Deutsche Welle.
Chinese authorities operate strict Internet censorship with a so-called "Great Firewall of China" that blocks information the ruling Communist Party views as improper, unhealthy or a threat to their rule.
Amnesty International describes China as one of the world's "enemies of the Internet".
Last year China introduced new regulations relaxing general media curbs for foreign journalists in the run-up to the Games.
However, domestic journalists, who work under strict censorship, were not included in the measures to relax reporting restrictions, nor were they promised any greater Internet freedoms during the Games