UK on critical alert

(AP Photo/ Alistair Robertson/PA)

Britain is on critical alert.

A day after police found two cars packed with nails and gasoline parked on London streets, a Jeep Cherokee, in flames, rammed into Glasgow's airport. Officials say two men were inside and one was burned by the flames. There were no other reports of injuries as the SUV was blocked from a terminal by security barriers.

"This is being treated as a terrorist incident," said Scottish Police Chief Constable Willie Rae.

The incidents come just days after Gordon Brown took over the office of the prime minister from Tony Blair -- and a week before the anniversary of the July 7 London transit attacks, which killed 52 people.

The airport was shut down. In the U.S., the Homeland Security department said it was increasing security over the July 4th holiday period.

AP reporter Ian Stewart, reporting from Glasgow, has more in this story.

--Ryan Pearson