Fans who bought tickets for synchronised swimming at this year's London Olympics could end up going instead to glamour events such as the showcase men's 100 metres athletics final because of an administrative error.

Organisers said on Wednesday that due to human error about 10,000 too many tickets had been sold in the second online offering last year, affecting thousands of purchasers who had been asked to swap events.

As a result of finalising the seating configurations in our venues and reconciling the millions of Olympic and Paralympic ticket orders against the seating plans for around 1,000 sporting sessions, we have discovered an error in seats available in four Synchronised Swimming sessions, a spokesperson said.

In December we contacted around 3,000 customers who had applied for tickets in the four sessions during the second round sales process.

We are exchanging their synchronised swimming tickets for tickets in other sports that they originally applied for.

A spokesman said the swap could involve a few hundred tickets for sessions such as the 100 metres final or swimming medal heats.

Although the glamour events sold out immediately in the first round of ticket sales, some highly desirable seats have been held back for sale in May this year once venues have been properly tested and positions confirmed.

The seats being swapped for the synchronised swimming will come from that final batch of around a million tickets.

The spokesman said ticket holders contacted by email and telephone had been understanding of the mistake and also appreciative of organisers' efforts to ensure they could still go to events.

Many of those who bought synchronised swimming tickets, which were not sold out in the initial ballot, in the second offering were likely to have done so in the hope of attending an Olympic event rather than as keen followers of the sport.

Tickets for the Olympic soccer tournaments remain on sale until February and will be made available again in the English spring if they do not sell out.

There will also be a first chance from Friday through to February 3 for British-based fans to resell legally any unwanted tickets online through their ticketing account.

(Reporting by Alan Baldwin, editing by John Mehaffey)