By DPA
London : Britain was on its highest security footing Sunday as authorities investigating the attempted car bomb attacks in Glasgow and London said they had arrested five people, and a controlled explosion was carried out at a Scottish hospital.
The explosion was carried out at the Royal Alexandria hospital in Paisley, close to Glasgow, where one of two men detained in connection with the previous day's bomb attempt on the city's airport remained in critical condition having sustained severe burns.
Police described the explosion as a precautionary measure, confirming that the vehicle was connected to the previous attacks but insisting they did not believe it contained explosives.
The 4×4 vehicle used in Saturday's failed attack had contained un-detonated propane gas cylinders in an echo of Friday's twin car bomb attempts in London.
Earlier police said a 26-year-old man was arrested in connection with a "suspicious vehicle" close to Liverpool, whose airport was briefly shut down on Saturday evening.
That arrest followed an operation on the M6 motorway in Cheshire which resulted in a 27-year-old man and a 26-year-old woman being taken into custody. The two were brought to London for questioning.
British police were during the course of the day also searching for terrorism suspects at several houses near Glasgow airport, local media reported.
In an interview with the BBC Sunday, Prime Minister Gordon Brown said the failed car bomb attacks were attempts to kill many people and cause major damage.
The new prime minister, who replaced Tony Blair Wednesday, said that it is clear Britain is confronted by people with connections to the Al Qaeda terror network.
"The first duty of the government is the security and safety of all the British people, so it is right to raise the level of security at airports and in crowded places in the light of the heightened threat," the prime minister said.
Britain's threat level is "critical," the highest level and one that indicates that attacks are "imminent."
Brown warned that the terrorist threat will be "long-term and sustained" and he asked the public to be "constantly vigilant".
"We have to fight it in a number of different ways – militarily, by security, by police, by intelligence," Brown said. "We've got to also fight it as a battle of hearts and minds.
Lord Stevens, an adviser to the new British government, stated that there was a connection between terrorist activities in Iraq and recent attempts in Britain, the British Sunday News of the World reported.
The report cited Lord Stevens as saying Friday and Saturday's would-be attackers in Britain were using the same bomb-making techniques that are used in the current Iraq insurgency and in the Bali terrorist attacks in 2005.
The British adviser said that it was not credible that disaffected young British Muslims were simply learning terror methods over the internet, but rather the tactics were being "imported from Baghdad".
On Saturday a Jeep Cherokee was driven into the curbside doors of Glasgow airport's terminal building. The vehicle burst into flames as it crashed into the glass front doors of the check-in terminal about 3.15 p.m. (1415 GMT) but it did not fully explode.
The car did not completely enter the terminal building, but the ensuring fire did extensive damage. One person was slightly injured.
One of the two suspects arrested after climbing out of the blazing Jeep was being treated at Paisley's Royal Alexandria Hospital.
Scottish Police Chief Constable William Rae said the suspect had suffered severe burns and was in critical condition. Witnesses said that the man's hair and much of his clothes and skin were burned off.
The second suspect arrested at the airport was being held at high-security Govan police station.
Scottish police said late Saturday that the attack on Glasgow airport seemed linked to Friday's two foiled car bombings in London.
"There are clearly similarities," Rae told a press conference. "And we can confirm that this is being treated as a terrorist incident."
In both the London and Glasgow attacks, automobiles appeared to have been rigged as fuel-air bombs, fuelled by both petrol and propane gas.