Beijing - Soldiers operating the huge scroll that formed the centrepiece of last week's Olympic opening ceremony had to stay hidden under the structure for up to seven hours, wearing nappies because they were not allowed toilet breaks, state media reported on Friday.

Nearly 900 soldiers were hidden underneath the scroll, many of them moving giant printing blocks with Chinese characters, the Beijing News reported.

"The performers for Chinese character parts went into the models underground at 2 pm, and after getting in there they could not come out," the newspaper quoted choreographer Han Lixun as saying.

"The underground area was so hot, there were 897 people there, and they had to wait until they finished their performance," Han said.

"So altogether they had to stay there for six to seven hours, and they could not even go to the toilet, so they all wore nappies," Han said.

Asked by the newspaper why the soldiers had to be in place so early, Han said it was because of the complexity of getting all the performers into position before spectators began entering the 91,000-seat Bird's Nest Olympic stadium.

"With all the spectators coming into the stadium, the performers have to prepare in advance," he said.

"Every performer should stay in a fixed place at a fixed time," Han said.

The spectacular Chinese-style opening ceremony last three-and-a- half hours and was directed by award-winning film-maker Zhang Yimou.

After the ceremony, organizers admitted that part of the fireworks display shown on television was actually an animation recorded in advance.

They also said a girl whose song during the ceremony won wide praise did not actually appear in the stadium and her song was mimed by another girl who was considered more attractive to foreign audiences.

Almost one third of the world's population - a little over 2 billion people - watched the ceremony, according to the global market research company Nielsen on Thursday. (dpa)