Aircraft that enter restricted airspace illegally during the Olympics may be blown out of the sky, the Royal Air Force has said.

RAF Typhoon fast jets and RAF Puma helicopters with snipers armed with hi-tech rifles will be among the military aircraft patrolling the restricted zone which comes into force from Saturday.

"As a last resort, we will have lethal force as an option," said Air Vice-Marshal Stuart Atha, the Olympics air security commander.

Asked who would give the order for lethal force to be used, AVM Atha said: "The highest level of Government makes that decision."

He said taking lethal action would be a "worst-case scenario" and that a best-case scenario would be to intercept and gain knowledge of the seriousness of the situation away from the built-up area of London.