LONDON (Aug. 10) - British police said Thursday they had arrested 21 people in connection with a terror plot against airlines traveling from Britain to the U.S. which was "intended to be mass murder on an unimaginable scale."
London's Heathrow airport, the busiest airport in Europe, was closed to most European flights Thursday morning after officials raised Britain's national security alert to its highest level - suggesting a terrorist attack may imminent. Huge crowds formed at security barriers.
Police carried out the arrests overnight in London, its suburbs and Birmingham as part of a major covert counterterrorism operation that had lasted several months, Deputy Commissioner Paul Stephenson said. The identities of those arrested were not immediately released.
Police said searches were continuing in a number of locations.
"We have been very successful in arresting those we were targeting but this is a lengthy operation, and no doubt there will be further developments," Stephenson told reporters outside the headquarters of the Metropolitan police.
"We think this was an extraordinarily serious plot and we are confident that we've prevented and attempt to committee mass murder on an unimaginable scale," he said.
He declined to how many aircraft may have been targeted, or which airports might have been involved. He also refused to say whether the suspects were British citizens or foreigners.
Prime Minister Tony Blair, vacationing in the Caribbean, had briefed President Bush on the situation overnight, Blair's office said. There was no immediate public reaction from the White House. Bush is spending a few days at his ranch near Crawford, Texas.
Britain's 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."
The U.S. government responded to the announcement by raising its threat alert to its highest level for commercial flights from Britain to the United States amid fears the plot had not been completely crushed.
"We believe that these arrests (in London) have significantly disrupted the threat, but we cannot be sure that the threat has been entirely eliminated or the plot completely thwarted," said U.S. Homeland Security Secretary Michael Chertoff.
It is the first time the red alert level in the Homeland Security warning system has been invoked, although there have been brief periods in the past when the orange level was applied. Homeland Security defines the red alert as designating a "severe risk of terrorist attacks."
Chertoff added, however, there was no indication of current plots within the U.S.
A senior U.S. counterterrorism official said authorities believe dozens of people - possibly as many as 50 - were involved in the plot, which "had a footprint to al-Qaida back to it." The official spoke on condition of anonymity because of the sensitivity of the situation.
The plan involved airline passengers hiding masked explosives in carry-on luggage, the official said. "They were not yet sitting on an airplane," but were very close to traveling, the official said, calling the plot "the real deal."
Passengers in Britain faced delays as tighter security was hastily enforced at the country's airports and additional measures were put in place for all flights. Laptop computers, mobile phones, iPods, and remote controls were among the items banned from being carried on board.
Liquids, such as hair care products, were also barred, raising the possibility that authorities were searching for a liquid explosive.
"I'm terrified really, I'm really scared," said Sarah Challiner, 20, who was waiting to board a flight from Manchester's airport.
Hannah Pillinger, 24, seemed less concerned by the announcement. "Eight hours without an iPod, that's the most inconvenient thing," she said, waiting at the Manchester airport.
Most European carriers canceled flights to Heathrow because of the massive delays created after authorities enforced strict new regulations banning most hand baggage.
Heathrow's block on incoming traffic applied to flights of three hours or less, affecting most of the incoming traffic from Europe, an airport spokesman said on condition of anonymity in line with airport policy.
Officials at Frankfurt's airport, Europe's second-busiest, Schiphol in Amsterdam and Charles De Gaulle in Paris said Heathrow-bound planes could instead land at their airports if they needed to.
London's Heathrow airport was the departure point for a devastating terrorist attack on a Pan Am airplane on Dec. 21, 1988. The blast over Lockerbie, Scotland, killed all 259 people aboard Pan Am Flight 103 and 11 people on the ground.
The explosive was hidden in a portable radio which was hidden in checked baggage.
A Scottish court convicted Libyan intelligence agent Abdel Basset Ali al-Megrahi of the bombing in 2001 and sentenced him to life imprisonment. A second Libyan was acquitted.
In 2003, Libya officially accepted responsibility for the attack and agreed to pay relatives of each bombing victim at least $5 million.