The U.S. government has raised its security threat level in response to a reported terrorist plot in Britain. British officials said Thursday they have arrested more than 18 people planning to blow up planes flying from Britain to the United States.
The U.S. government raised its threat level early Thursday to "severe or red," the highest level for commercial flights from Britain to the United States. It also stepped up the general level of security for all flights within the United States.
U.S. Homeland Security Secretary Michael Chertoff said arrests made in London have significantly disrupted the terrorist threat, but that it is as yet uncertain that the threat has been entirely eliminated.
The statement said there is no indication of a plot within the United States.
The U.S. measure came after British officials said they had thwarted a plot to blow up passenger aircraft in flight, using explosives hidden in hand luggage.
British Home Secretary John Reid said those involved in the terror plot intended to bring down several aircraft bound for the United States.
"Overnight the police, with the full knowledge of ministers, have carried out a major counter-terrorism operation to disrupt what we believe to be a major threat to the U.K. and international partners," he said. "The police, acting with the Security Service MI5, are investigating an alleged plot to bring down a number of aircraft through mid-flight explosions, causing a considerable loss of life. The police believe the alleged plot was a very significant one indeed."
Britain has raised its national public security threat level to "critical" - the highest category, which means an attack is expected imminently.
Authorities are dramatically stepping up security measures at British airports. Among other things, passengers will not be able to bring any hand baggage with them on planes departing from any airport in Britain. Authorities are allowing passengers to board flights carrying only bare essentials, such as passports and wallets.
Officials say the measures are designed to allow air travel to continue as much as possible, but are expected to cause considerable delays.