The first full dress rehearsal for the opening ceremony of the Olympic Games was held under strict secrecy on Thursday.

State media report that the police had three layers of cordon fences around the Bird's Nest to avoid leaks about program content.

Participants and stadium workers were asked to sign confidentiality agreements, Xinhua said.

The 3 1/2-hour event will be directed by Zhang Yimou. Last minute changes to the program, Xinhua said, included a tribute to the rescuers and victims of the May 12 Wenchuan earthquake in Sichuan.