Chinese officials admit journalists covering the Beijing Olympics will not have completely uncensored internet access.
Chinese and Olympic officials say sites related to the spiritual group Falun Gong would be blocked. Journalists also found they could not see some news or human rights websites.
China enforces tough internet controls, but said when it bid for the Games that journalists would be free to report.
A senior international Olympic official called the move disappointing. But International Olympic Committee press commission chairman Kevan Gosper confirmed that officials had been aware of it.
He told the South China Morning Post: "There will be full, open and free internet access during Games time to allow journalists to report on the Olympics.
"But I have also been advised that some of the IOC officials had negotiated with the Chinese that some sensitive sites would be blocked."
More than 20,000 foreign media personnel are due in the Chinese capital to cover the Olympic Games, which begin on 8 August. Many are already moving into the press and broadcast centres in Beijing.
On Tuesday, they were unable to access the website of Amnesty International as it issued a report criticising China's human rights record.
Journalists said some international news pages and sites that dealt with issues such as Tibet were also inaccessible.