A deal with Beijing has allowed the Chinese authorities to block sensitive internet sites, the International Olympic Committee has disclosed.

Journalists at the main media centre in Beijing found that the BBC Chinese language site was inaccessible, as were the websites of human rights organisations such as Amnesty International and Reporters without Borders — whose welcome page at present shows the five Olympic rings replaced with interlocking handcuffs. The US broadcaster Radio Free Asia and the German radio station Deutsche Welle are also out of bounds.

Kevan Gosper, the head of the International Olympic Committee (IOC) press commission, confirmed that some of its officials had agreed to Chinese demands that some sensitive sites be blocked on the ground that they were not related to the Olympics.

“I regret that it now appears Bocog [the Beijing Organising Committee] has announced there will be limitations on website access during Games time.” While the censors have allowed access to the online encyclopaedia Wikipedia, attempts to read entries about the 1989 Tiananmen Square massacre were unsuccessful. Computers at the main press centre displayed the message: “Impossible to display the page.”

Giselle Davies, of the IOC, said that officials had been told repeatedly by Beijing organisers that some sites would be unavailable to the 20,000 reporters covering the games. “We’re working with them to ensure the media face the minimum possible restrictions.”

Chinese organisers said that the censorship would not hamper journalists in their job of reporting on the Games. Sun Weide, a Bocog official, said that the plan had always been to provide “sufficient” internet access for foreign reporters. Sites run by the Falun Gong religious sect remain inaccessible, as do most sites with the word Tibet in their internet address.

The revelation that China’s censors had never considered relaxing internet curbs further tarnishes the image of the Games amid persistent fears of pollution and security so tight that cafés are not allowed to place tables on pavements and hotels cannot change their brand of shower gel without checks.

China is clearly determined not to allow any disruption to the August 8-24 Games, and has announced a sweeping security operation in Lhasa to prevent anti-Chinese unrest. Security in the Tibetan capital has been tight, with paramilitary People’s Armed Police patrolling the streets, since a deadly riot on March 14 when Tibetans rampaged through the town setting fire to shops and attacking ethnic Han Chinese.

Officials refuted a report that two monks had been killed in a clash this month with police in a monastery in a Tibetan area of western China. They said that the men had died when a room in which they were having lunch collapsed as 50 kilograms (110 pounds)of an unidentified black powder exploded, ignited by faulty electrics.