Journalists say the development reverses an earlier pledge to remove China's censorship firewall during the games, which begin on Friday week.
A spokesman for the Chinese organising committee said sites linked to the banned Falungong spiritual movement and other unspecified ones would remain blocked for foreign reporters covering the Games.
The head of the International Olympic Committee's press commission, Kevan Gosper, told reporters that he would take the matter up with the Chinese authorities.
