Armed police have been introduced at two nuclear power stations in Suffolk amid security fears.
Armed officers will patrol at the Sizewell sites
Civil Nuclear Constabulary officers have been drafted in to patrol Sizewell A and B near Leiston.
Security was reviewed following the 11 September attacks in America and stepped up following the London bombings in July.
Sizewell B director Mark Gorry said the move was intended to boost confidence and act as a deterrent.
He said: "We now have an armed contingent on the site."
A spokeswoman for British Energy, which operates Sizewell B, confirmed that armed officers had recently started to patrol the site.
And a spokesman for British Nuclear Group, which runs Sizewell A, said that security had been reviewed in the light of terrorist attacks.
A Civil Nuclear Constabulary spokeswoman added: "Security at sites is kept under constant review and is not introduced in response to any particular event or attack."
Greenpeace campaigners have breached security at Sizewell B twice in the last few years to highlight what they claim is Sizewell B's poor security and vulnerability to terrorist attack.