British authorities said yesterday they had thwarted a terrorist plot to simultaneously blow up several aircraft en route to the US using explosives smuggled in hand luggage, averting what police described as "mass murder on an unimaginable scale."
Officials raised security to its highest level -- suggesting a terrorist attack might be imminent -- and banned hand-carried luggage on all trans-Atlantic flights. Huge crowds formed at security barriers as officials searching for explosives barred nearly every form of liquid outside of baby formula.
"This was to be a simultaneous attack on multiple targets, targeting US-bound aircraft," a police official said, speaking on condition of anonymity because of the sensitivity of the case.
The extreme measures at one of the world's largest aviation hubs sent ripples throughout the world. Heathrow airport was closed to most flights from Europe.
The US government responded by raising its threat assessment to its highest level for commercial flights from Britain to the US amid fears the plot had not been completely crushed. Terrorists had targeted United, American and Continental airlines, two US counterterrorism officials said.
Police were confident they had disrupted a plot against aircraft which was "intended to be mass murder on an unimaginable scale," Deputy Police Commissioner Paul Stephenson said yesterday.
Police arrested 21 people in London, its suburbs and in Birmingham, central England. Searches continued in a number of locations.
The suspects were "home-grown," though it was not immediately clear if they were all British citizens, the police official said, adding that police were working with the South Asian community.
British Prime Minister Tony Blair, vacationing in the Caribbean, briefed US President George W. Bush on the situation overnight, Blair's office said.
British Home Secretary John Reid said the alleged plot was significant, and that terrorists aimed to "bring down a number of aircraft through mid-flight explosions, causing a considerable loss of life."
Passengers faced delays as tighter security was hastily enforced at the country's airports. British Airways said some flights were likely to be canceled. Laptop computers, mobile phones and iPods were among the items banned from being carried on board.
Liquids, such as hair care products, were also barred and Chertoff's statement raised the possibility that authorities were searching for a liquid explosive.
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