Irate Olympics organisers yesterday threatened to take action against a South Korean TV network that released an unauthorised sneak preview of the opening ceremony's gala show - regarded as a top national secret on the mainland. The two-minute footage offered viewers a brief but tantalising peek at what to expect in the 31/2-hour opening ceremony - which has taken thousands of people more than three years to prepare and has been guarded with tight security - on August 8. The footage, which first appeared in a programme on the South Korean TV station SBS, was quickly picked up by several websites including the popular YouTube. It was not clear how SBS - one of South Korea's four major TV stations - obtained the footage from the 'Bird's Nest' stadium. But the Beijing Organising Committee for the Olympic Games (Bocog) was not impressed. 'We are deeply upset by the leak,' said Wang Hui, a Bocog spokeswoman. 'We believe this [was done by] stealth, because we have never invited any media guests for the rehearsals ... We don't rule out further actions against the broadcaster.' The International Olympic Committee also joined in the condemnation last night. 'We understand people's eagerness to get a sneak preview of spectacular events. But we also call for the media's respect for all the efforts we put in to keep this secret,' IOC spokeswoman Giselle Davies said. Mainland authorities have ordered all mainland websites that carried the footage to delete it. The Communist Party's Publicity Department ordered media outlets to stop speculating about the opening ceremony and the gala show. The show's contents have been guarded closely to retain the element of surprise. People involved in it have had to sign confidentiality agreements. Any breach could result in jail sentences of up to seven years, according to a mainland media report. Some parts of the opening ceremony have had to be revised because a senior leader who attended the dress rehearsal on July 17 was not satisfied and ordered changes to be made, sources familiar with the situation said. It was not clear which parts had been changed, or why.