Police and the military in London have been put on high alert over the weekend because of fresh warnings that Britain is a likely target for terrorist attacks.
The number of officers on high-visibility patrols in the capital will be boosted by 500 to 1,500 during the next two days.
Intelligence reports during the past week have suggested that an attack on the UK was being planned. Sources have told The Independent that the threat is "non-site specific", with no individual targets being identified.
Both the Metropolitan and City of London Police are operating on an "amber" security level – the highest after "red", although they stress there is no specific intelligence to suggest that London is at risk.
Police presence has been increased across the city, particularly at government buildings and City institutions, and checks on traffic stepped up. Security at power and water supplies has also been tightened.
Downing Street has constantly played down fears of the prospect of atrocities in Britain, repeating its carefully worded statement that "we have no evidence of a specific threat to the UK".
However, the FBI warned on Thursday night that fresh terror attacks could be launched within the next "several days". John Ashcroft, the Attorney General, was briefed that the likelihood of further incidents was "100 per cent".
Peter Hain, a Foreign Office minister, found himself in trouble with Downing Street last month when he let slip that Osama bin Laden was planning more "high-impact" atrocities. Mr Hain told a television audience he had seen intelligence reports containing evidence that Britain faced a "very dangerous situation" from the suspected terrorist.
As if to underline the US assessment of the threat, the American embassy in London put up a double row of steel barriers around its Grosvenor Square premises on Friday and barred passing traffic.
Britain's plans for dealing with an emergency in London would be overhauled in response to the terrorist attacks on New York and Washington, the Government said.
Nick Raynsford, the local government minister, and Ken Livingstone, the Mayor of London, met senior officials from the capital's emergency services to review the plans. A special civil contingencies committee for London has been established and will report to emergency planners in Whitehall.
Mr Livingstone said: "Since the events in New York, all of the existing plans have been reviewed and updated in the light of the attacks, which I don't think anyone anticipated in terms of terrorism."
Speaking before the meeting, Mr Raynsford denied that the capital's emergency planning had been neglected before September's terrorist attacks, insisting that all services were working together to ensure that the city was ready for any emergency.
The Local Government Association said there was no need for gas masks, protective suits or other precautions in the light of the terrorist attacks, but said that local authority planners were continuously reviewing arrangements to deal with major incidents.Reuse content