GCHQ is set to play a vital role in protecting the London Olympic Games from terrorist attacks.

The Benhall-based intelligence base will team up with other secret services to feed information to a central Olympic Intelligence Centre.

GCHQ, which employs more than 4,000 people at its Doughnut headquarters in Cheltenham, is responsible for intercepting terrorist communications.

It will work alongside MI5, MI6 and regional police forces in the Olympic Intelligence Centre, with its role expected to grow during the run-up to the Games in 2012.

The new body will be responsible for putting in place security measures to protect all Olympic venues.

Security surrounding the event will probably be the largest policing operation the country has ever experienced, with more officers than the 12,000 involved in the 2005 G8 summit.

Chris Allison, assistant commissioner at the Home Office, told a national newspaper everything possible was being done to ensure the Games passed without incident.

He said: "There are always going to be people talking about it.

"People do want reassurance. They want to know what measures are in place and that steps are being taken to guard against an attack."

Among the measures being proposed is a 'no-fly zone' over the main Olympic Stadium in East London to prevent terrorists using light aircraft as missiles.

Other threats for which security services are preparing include car bombs, planted bombs and suicide bombs.

Security for the event will cost the taxpayer an estimated £600 million and already includes a specialist team which polices the Olympic site.

Nine million spectators are expected to visit the 34 venues across London once the Games get underway, alongside an unknown number of private events.

The Government has set up an Olympic and Paralympic Security Directorate within the Office for Security and Counter-Terrorism, with the mandate to look at all possible threats to the Games.

It is now working with police and Olympics organisers to ensure venues include as many security features as possible in their design.

It is hoped the measures could help to minimise the effect of any chemical, biological, radiological or nuclear attacks.

Despite the terrorism fears, officials are confident they will be prepared and have promised the public that the atmosphere of the Games will not be affected.

A GCHQ spokeswoman said she was unable to comment on the centre's role in protecting the event.