Soldiers were drafted in to fill empty seats at a number of Olympic venues, including the Aquatics Centre and gymnastics arena after prime blocks went unused.
Sponsors not taking up their allocation of seats were blamed for most of the no-shows but international media and competitors' families were also accused of not attending.
The move came as Britain finally got on the medal table yesterday when cyclist Lizzie Armitstead won silver in the women's road race and swimmer Rebecca Adlington took bronze in the women's 400m freestyle.
Sports fans across Britain, who struggled to get tickets, have been outraged by footage of empty seats at venues including Wimbledon, where yesterday Andy Murray won his opening tennis match.
London Organising Committee of the Olympic and Paralympic Games (Locog) chairman Sebastian Coe, who threatened to name sponsors that did not fill their seats, said missing spectators were mostly officials from international sports federations, other Olympic officials and their families and friends.
"It doesn't obviously appear to be a sponsorship issue at the moment," Lord Coe said, after Culture Minister Jeremy Hunt said he thought the vacant seats had belonged to sponsors.
As the row mounted, Lord Coe said only 8% of allocated tickets went to big corporate sponsors such as Visa and Coca-Cola and 75% of tickets were in the hands of the public. "I don't think you will be seeing this as an issue, long-term through the Games," he said.
Organisers would fill some of the seats with servicemen and women, as well as local students and teachers, he said. And they would sell more tickets – as they did with about 1000 tickets on the London 2012 website on Saturday night. He said a system had been introduced similar to the one used at Wimbledon, where people coming out of the stadium handed on their tickets so the seats could be made available to others.
Locog said it would examine options to upgrade the tickets of members of the public and move them into accredited areas.
Sponsors PG, Visa, McDonald's and Coca-Cola have all issued statements reassuring officials, fans and athletes that their allocated tickets have been and will be used by winners of promotional contests, partners, customers and employees. "All of our guests are incredibly excited to be able to be a part of London 2012 and we believe usage levels of our tickets have been extremely high so far," Coca-Cola said.
However, more vacant seats were reported yesterday. Troops were despatched to the North Greenwich Arena yesterday morning by Locog to take up seats left empty by accredited officials from Olympic and sporting federations, as well as some sponsors and members of the media.
More troops, many of whom had their leave cancelled to provide emergency cover after the organisers failed to find enough security guards, will be issued with last-minute invites to take seats in venues when blocks of seats are found to be empty, the games organisers said.
At yesterday's first session of the men's basketball at the 12,000-capacity basketball arena, 70% of the lower tier of seats – which includes those allocated to sponsors, Olympic officials and athletic federations – was empty. About 15% of the larger upper tier, sold to the public, was empty. "We've got a few empty seats, so please shout twice as loud for those empty ones," announcer Ian Oswald said at one men's weightlifting event.
Empty seats were reported at the women's gymnastics, particularly close to the mat. Some 100 soldiers, apparently who had been on security duty, occupied some of the empty chairs.
Seats were also vacant at the eventing dressage despite the appearance of Zara Phillips, the Queen's granddaughter, who is part of the British team.
Although fencing and boxing were fairly full, there were sections of empty seats at the canoe slalom. And at Wimbledon for tennis a large number of seats stood empty with stickers saying "athlete" and others that were designated for Olympic sports officials.
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