LONDON - Britain raised its national threat level to "critical" Saturday amid fears of a new Al-Qaeda-style attack, after police said they were treating three failed car bomb attacks in two days as connected.
Scottish police confirmed that an incident Saturday in which a blazing car ploughed into the main terminal at Glasgow airport was being considered as terrorism, and as linked to a double car bomb plot thwarted in London Friday.
"I can confirm that we believe the incident at Glasgow airport is linked to the events in London yesterday," said Chief Constable Willie Rae, briefing reporters on the incident earlier in the day.
In a potentially disturbing detail, he also revealed that a "suspect device" was found on one of two men arrested after the attack, when he was taken to hospital to be treated for severe burns.
Prime Minister Gordon Brown, facing a baptism of fire just days after taking office, explained the decision to raise the threat level to "critical" after a fresh meeting of the government's COBRA crisis cell.
"Critical" is the highest on a five-level scale, and means another attack is expected "imminently."
"The first duty of a government is the security and safety of all the British people," Brown said. "So it is right to raise the levels of security at airports and in crowded places in the light of the heightened threat."
Amid fast-moving events, Liverpool's John Lennon airport was closed also until further notice after the attack in Glasgow, in which a burning jeep was driven into the main terminal at Scotland's busiest airport.
In the United States the White House also announced that security was being beefed up at US airports, although a spokesman said there was "no indication of any specific or credible threat to the United States."
The developments came exactly a week before the second anniversary of the July 7, 2005 suicide bombings on London transport which killed 52 people during the morning rush-hour.
The latest string of foiled attacks began in the early hours of Friday when two Mercedes cars were found abandoned in London's entertainment, packed with gas cannisters and nails.
Police launched a major manhunt immediately after the first car was found, and on Saturday Sky News reported that CCTV footage had provided "crystal clear" images of a man running away from the car outside a London nightclub.
The second car was left parked nearby, also in the early hours of Friday, but it was given a parking ticket and towed away to a car pound. It was only there that the explosives were found after police were alerted later Friday.
One witness quoted by the BBC said that some 500 people were in the club when the first car bomb was spotted by alert guards around 1:30 am -- shortly before the club was to close, spilling revelers out onto the street.
In Saturday's Glasgow attack, two men described by some eyewitnesses as of "Asian" appearance drove a jeep-style vehicle into the front of the main terminal.
Witnesses said one of the men with his clothes on fire left the vehicle and was restrained by members of the public. The flames were put out with a fire extinguisher, and the pair were arrested, one of them being taken to hospital.
At a news conference later, Chief Constable Rae said a "suspect device" was found on him while he was being treated for severe burns at the hospital, which was partly evacuated as a result.
He refused to respond to a question about whether the "suspect device" was a suicide belt, but added: "It was on his person."
In London security was ratcheted up with increased police patrols on the streets, in particular as hundreds of thousands of people turned out for the city's annual Gay Pride march.
But London Mayor Ken Livingstone insisted Londoners would not be deterrred.
"I think people are completely safe to walk about the streets of London today and tomorrow," he told BBC radio. "I have promised my family all week that we are all going on the Gay Pride march. We will all be there."
At Wimbledon security was tightened up at the famous tennis championships, with systematic checks on all vehicles entering the car parks and on everyone coming in to the tournament.
Chillingly, a message posted in an Internet chat room shortly before the attacks were foiled appeared to indicate an Islamist link.
"London shall be bombed," said the 300-word posting on the Al-Hesbah chat room -- sometimes used by Al-Qaeda -- left by a person identified as Abu Osama al-Hazeen, CBS News reported.
Pauline Neville-Jones, former head of the government's joint intelligence committee, agreed that a link with the terror network was likely.
"I will be inclined to believe there is some kind of Al-Qaeda link," she told the BBC, adding that it appeared "aimed at the new government."

06/30/2007 21:38 GMT