'The man was on fire, like a scene from a horror film'

Britain was on maximum alert last night after a burning 4x4 Jeep Cherokee was rammed into the terminal building at Glasgow airport, triggering fears that the two failed car bombs in London marked the start of an organised terror campaign.

With Britain in the grip of a new wave of terror attacks, the Government raised its threat assessment to "critical", the highest level indicating that further attacks are imminent.

Yesterday afternoon, passengers waiting to check in for flights from Glasgow scattered as the blazing vehicle, said to have two Asian men inside, smashed into the building at speed and became jammed in an entrance at 3.11pm. According to witnesses, one man climbed out and tried to throw more petrol on the flames from a canister, while the other sought to force the Jeep further into the terminal as people ran screaming from the scene.

"There was absolute chaos," said a witness, James Edgar. "[The driver] was very close to getting to a place that was holding maybe 200 people. There was no emotion on his face whatsoever. The crowd were shouting at him, but he just stared straight ahead."

Police raced over and struggled with the two men, one of whose clothes were on fire. "He looked like something from a horror film," said Robin Patterson, from Rochester in Kent. "His skin was peeling, his hair was all burnt. You couldn't see what colour he was, just that he was a big man." According to onlookers, the man briefly struggled free and tried to open the boot of the vehicle before he was finally dragged away.

Police said last night there had been no intelligence prior to the incident that Scotland was about to be attacked. They said they were treating the incident as a terrorist attack and that it was linked to the failed car bombings in London on Friday.

Chief Constable Willie Rae of Strathclyde Police said two men were arrested following the incident. One man, with severe burns, was taken to the Royal Alexandra Hospital in Paisley. The emergency department there was then evacuated after a "suspect device" was discovered on him. The man is said to be in a critical condition. Police would not elaborate on the nature of the device, but said it was being investigated and all areas of the Royal Alexandra had later been reopened. Amazingly, only one other person, who was treated for a leg injury, was hurt in the incident.

At Glasgow airport, which last night remained closed, fire crews struggled to put out the fiercely burning Jeep, with the flames spreading to part of the canopy above the pavement outside the terminal. The Jeep, described by police as in a "highly unstable condition", was still at the scene.

Last night hundreds of passengers were left stranded at the airport, many of them on planes delayed from taking off or unable to disembark passengers after arrival. Among them was the sister of Liam Fox, the Conservative shadow defence secretary, and her family. Passengers were told they would not be allowed off the planes until police had conducted a thorough search of the building.

The drama worsened national jitters caused by news the previous day that two "viable" car bombs, which would have caused carnage had they exploded, had been discovered in London. Later Blackpool airport was closed by police. The set-down road to Birmingham airport was also closed and there were several other brief alarms.

Yesterday afternoon Scott Leeson was waiting for a colleague on an arriving flight in Glasgow. "Fortunately his plane was delayed," he said. "There were a couple of explosions. My main concern was to ring my colleague with his young family. He would have been coming out of that door had his plane not been delayed. There was a lull at that point, and there weren't as many people around. If it had happened 10 minutes earlier, there would have been fatalities."

Gordon Brown, confronted with a terror crisis immediately on taking office as Prime Minister, last night chaired the second emergency meeting in 24 hours of the Government's Cobra security co- ordination committee. Afterwards he said, "I know that the British people will stand together, united, resolute and strong."

Terror analysts said the authorities' first concern would be to establish whether the Glasgow incident was related to the attempted bombings in London or was a hastily improvised attack.

The Home Secretary, Jacqui Smith, said after the Cobra meeting: "I can confirm that the Joint Terrorism Analysis Centre has raised the national threat level to critical. Critical is the highest level of threat, and the threat level will be closely reviewed on a regular basis. Appropriate security measures have been put in place."

Experts believe the Government may extend police powers to stop and search members of the public in areas under possible threat, such as railway stations.

The last time the threat level was raised from "severe" to "critical" was in August last year, when transatlantic flights were disrupted by a terror warning. The level was reduced after four days, but restrictions on air passengers remain in place.