Rehearsal footage of the Olympic opening ceremony was removed from YouTube on Wednesday as organisers stepped up efforts to keep details of tomorrow's eagerly awaited curtain-raiser under wraps.

Some spectators published video online of last night's sneak preview of the £27 million spectacular despite an appeal from the show's artistic director, Danny Boyle, not to spoil the surprise.

Recordings of the ceremony were removed from the website on "copyright grounds", while Twitter users were urged to report any leaked footage of the rehearsals.

One video on YouTube - entitled "Olympic 2012 opening ceremony snapshot from rehearsal" - was replaced with a message stating: "This video contains content from International Olympic Committee, who has blocked it on copyright grounds."

Another video, named "Olympic Opening Ceremony Rehearsal", was "removed by the user", according to the site.

A YouTube spokeswoman said: "As always, when we're notified that a particular video uploaded to our site infringes another's copyright, we remove the material in accordance with the law."

Games organisers asked thousands of people who were invited to two sneak previews of the ceremony to refrain from circulating any revealing pictures or videos taken inside the Olympic Stadium.

Film director Boyle reportedly addressed the audience during the technical and dress rehearsals and called on them to "save the surprise" by not posting any images on social networks.

The hashtag "#savethesurprise" was also emblazoned on giant screens inside the Olympic Stadium, according to people at the event, before trending globally on Twitter.

Boyle and his creative team have done their best to keep details of the opening ceremony secret and it seemed that most spectators have followed their wishes by not revealing any of the show's big surprises.

Alex Balfour, head of new media for the Olympic and Paralympic Games, tweeted: "If you want to #savethesurprise and see vids of Olympic dress rehearsal on YouTube email the links to monitoring@olympic.org."

The opening ceremony, which is expected to be watched by billions worldwide, received hundreds of other glowing reviews from those lucky enough to be at the rehearsal.

An audience of about 62,000 is expected in the stadium, in Stratford, east London, for tomorrow night's performance, which will feature thousands of performers.

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