LONDON - More than 400 soldiers backed by tanks patrolled Heathrow International Airport and other potential terrorist targets yesterday in response to a "specific threat against the capital," the British government said.
Prime Minister Tony Blair, who officials said authorized the unprecedented security buildup at the airport, declined to provide details.
But Scotland Yard cited intelligence reports and noted that Osama bin Laden's al-Qaida terror network might try to use the Islamic festival of Eid al-Adha, which began yesterday, to mount attacks.
Officials said the precautionary measures taken at Heathrow, and at undisclosed transportation and economic centers in London that are considered vulnerable to attack, would continue for at least several days. Such vigilance at the airport had not been seen since an Irish Republican Army bombing campaign targeted the airport in the early 1990s, officials said.
The additional steps were taken less than a week after the assessment of the terrorism risk in the United States was elevated to one rung below the top level.
Chris Yates of Jane's Airport Review said the beefed-up security could be an effort to head off a surface-to-air missile attack like that aimed at a charter jetliner carrying Israeli tourists in Kenya last year.
"We can put all sorts of technology and security in airports, but it doesn't take an Einstein to work out that you can park around the perimeter and launch something like a missile," he said.
At Heathrow, Europe's busiest airport, Scimitar tanks with 30 mm cannons took up position around the airfield perimeter and on roadways leading to the passenger terminals.
Soldiers helped about 1,000 London police officers search vehicles entering the airport and bolster security at checkpoints.
"We're here to wreck any vehicle or force that creates trouble," said Lt. Richard Moger, a tank commander with the Household Cavalry Regiment based in Windsor.
Passengers responded to the spectacle with amazement and sometimes fear.
"This is not the England I know," said Elsie Williams, a senior citizen from Essex waiting for a flight to Kenya with her husband, Dennis. "It makes me feel shaky and terrible that the world has come to this."
Meanwhile, Islamic leaders in Britain reacted angrily to suggestions that the Eid al-Adha festival - which celebrates the end of the hajj, or annual Muslim pilgrimage to Mecca - was a factor in the new terrorism alert.
"It is like suggesting Christians would use Christmas to bomb Jewish, Muslim or Buddhist communities," said Massoud Shadjareh, chairman of the London-based Islamic Human Rights Commission.