U.K. Moves to 'Critical' Terror Alert

Updated from 6/30/2007

The U.K. has moved to a "critical" level of terror alert -- the nation's highest --after a burning car smashed into the main terminal building at Glasgow's airport Saturday.

The airport attack came just one day after police found two Mercedes containing explosives parked in downtown London, and a week before the second anniversary of terrorist bombings in London that left 52 people dead. Police have arrested five people in connection with the recent incidents, according to a BBC report.

U.K. Prime Minister Gordon Brown told the BBC Sunday that it was "clear that we are dealing, in general terms, with people who are associated with al Qaeda."

Brown added that people need to remain "constantly vigilant" against what is a "long-term and sustained threat."

Witnesses to Saturday's attack saw two men drive a burning Jeep into the terminal at Glasgow's airport, where it started a fire. Both men were arrested, although one suffered severe burns and is in the hospital in critical condition, according to the report.

Officials closed the airport, which is Scotland's largest, and suspended flights after the incident, but the airport is now reopening gradually, and some flights have arrived.