An anti-terrorism exercise has been carried out at the London Olympics Village, police confirmed.
The drill, staged over three days at the accommodation complex, involved the Metropolitan Police, other emergency services and the Ministry of Defence (MoD).
According to reports, live ammunition was fired as part of the exercise and the SAS was involved.
A spokesman for the Metropolitan Police said: "As part of a robust testing and exercising programme to ensure that multi-agency security arrangements for the Olympic Games are fit for purpose, an exercise was held at the Olympic Village.
"It was one of a series of counter-terrorism exercises involving the MoD, MPS and other emergency services. It was not held in response to any specific threat, but it is the latest live play exercise to be held within an Olympic venue as part of our preparations for the Games.
"Due to the nature of the exercise we are not prepared to discuss this in further detail."
A British Intelligence source told the Sun that the exercise "ran through the methods of dealing with an attack by terrorist gunmen intent on taking on hostages".
The source added: "To add to the sense of reality, live rounds were fired."
Eleven Israeli athletes and coaches were killed after terrorists took hostages at the 1972 Munich Games.