The links between three attempted car bombings in Glasgow and London are becoming "ever clearer", the UK's top counter-terrorism officer has said.
The links between the three attempted car bombings in Glasgow and London are becoming "ever clearer", the UK's top counter-terrorism officer has said.
Deputy Assistant Commissioner Peter Clarke said he was "absolutely confident" of uncovering details of the attackers' methods and network.
Deputy Assistant Commissioner Peter Clarke said he was "absolutely confident" of uncovering details of the attackers' methods and network.
A Jeep containing gas cylinders was driven into Glasgow Airport a day after two car bombs were found in London.
A Jeep containing gas cylinders was driven into Glasgow Airport a day after two car bombs were found in London.
Five people are being held, but police are thought to be hunting a suspect.
Five people are being held, but police are thought to be hunting a suspect.
BBC correspondent Daniel Sandford said that might explain why the country remained on its highest state of security alert - critical.
BBC correspondent Daniel Sandford said that might explain why the country remained on its highest state of security alert - critical, which means an attack is expected "imminently".
This means an attack is expected "imminently".
Police questioning
Scotland Yard said two people were arrested on the M6 in Cheshire overnight - a 26-year-old man and 27-year-old woman.
Two of those held by police are a 26-year-old man and 27-year-old woman who were arrested on the M6 near Sandbach, Cheshire, on Saturday night.
The man has been identified by the BBC as Dr Mohammed Asha, from Iran.
It is no exaggeration at all to say that new information is coming to light hour by hour Deputy Assistant Commissioner Peter Clarke
Another 26-year-old man was arrested in Liverpool. All have been taken to Paddington Green police station in London for questioning.
The man has been identified by the BBC as Dr Mohammed Asha.
'Outrage'
Both have been taken to Paddington Green police station in London for questioning.
Mr Clarke described the investigation into the failed bombings as "extremely fast-moving".
Another 26-year-old man arrested in Liverpool on Sunday remains in custody at a Merseyside police station.
He said: "It is no exaggeration at all to say that new information is coming to light hour by hour.
One of the two suspects held at Glasgow Airport on Saturday suffered severe burns and remains in a critical condition, and under armed police guard, at Royal Alexandra Hospital, in Paisley.
"I'm confident - absolutely confident - that in the coming days and weeks we will be able to gain a thorough understanding of the methods used by the terrorists, of the way in which they planned their attacks, and of the network to which they belong."
Glasgow - Burning car driven into doors of Glasgow Airport on Saturday. Two people arrested at scene London - Two car bombs that failed to detonate found in central London on FridayPaisley - Controlled explosion carried out on car at Royal Alexandra HospitalCheshire - Man and woman arrested overnight on M6, then taken to London for questioningLiverpool - Man arrested. Police searching two addressesHouston - Police searching houses in village near GlasgowNewcastle-under-Lyme - Police searching house in Staffordshire
Glasgow - Burning car driven into doors of Glasgow Airport on Saturday. Two people arrested at scene London - Two car bombs that failed to detonate found in central London on FridayPaisley - Controlled explosion carried out on car at Royal Alexandra HospitalCheshire - Man and woman arrested overnight on M6, then taken to London for questioningLiverpool - Man arrested. Police searching two addressesHouston - Police searching houses in village near GlasgowNewcastle-under-Lyme - Police searching house in Staffordshire
The BBC has learned those arrested are believed to be of varying Middle Eastern nationalities.
Mr Clarke earlier described the investigation into the failed bombings as "extremely fast-moving".
"It is no exaggeration at all to say that new information is coming to light hour by hour," he said.
"I'm confident - absolutely confident - that in the coming days and weeks we will be able to gain a thorough understanding of the methods used by the terrorists, of the way in which they planned their attacks, and of the network to which they belong."
He said forensic searches of vehicles were proving "extremely valuable" and thousands of hours of CCTV were being sifted through.
He said forensic searches of vehicles were proving "extremely valuable" and thousands of hours of CCTV were being sifted through.
Strathclyde Police issued the registration number of the Jeep used in the attempted airport attack on Saturday - L808 RDT - and appealed for information about sightings of the vehicle in recent weeks.
Elsewhere, Merseyside Police have been searching two addresses in the Liverpool area.
Assistant Chief Constable John Malcolm said the force was receiving about 100 calls an hour from the public.
And Staffordshire Police said its officers had been searching an address in Newcastle-under-Lyme with the West Midlands Counter Terrorism Unit and Met personnel.
The UK moved to its highest level of terror alert after the Jeep Cherokee crashed into the main doors of Glasgow Airport's main terminal and burst into flames on Saturday afternoon.
'Al-Qaeda links'
Prime Minister Gordon Brown told Andrew Marr on BBC One's Sunday AM it was "clear that we are dealing, in general terms, with people who are associated with al-Qaeda".
"It's obvious that we have a group of people - not just in this country, but round the world - who're prepared at any time to inflict what they want to be maximum damage on civilians, irrespective of the religion of these people who are killed or maimed," Mr Brown said.
Strathclyde Police issued the registration number of the Jeep used in the attempted attack on Glasgow Airport - L808 RDT - and appealed for information about sightings of the vehicle in recent weeks.
A controlled explosion was carried out on a car at the hospital where a suspect is being treated. It is thought to have been connected to the failed airport bombing, police said.
Searches have also taken place at addresses in Houston, Renfrewshire, close to the airport.
Glasgow Airport was fully opened on Sunday afternoon, almost 24 hours after the incident.
Assistant Chief Constable John Malcolm, of Strathclyde police, said the force was receiving about 100 calls an hour from the public.
"This reflects the outrage felt in our communities at this act, and the calls we are receiving are supportive of the police actions," he said.
"This reflects the outrage felt in our communities at this act, and the calls we are receiving are supportive of the police actions," he said.
Earlier Prime Minister Gordon Brown said the UK would not yield despite the threat from people associated with al-Qaeda.
Heightened security
The government's emergency response committee, Cobra, held its fourth meeting in three days.
The attempted airport attack came a day after two Mercedes containing petrol, gas cylinders and nails were found outside the Tiger Tiger club in London's Haymarket and a nearby street on Friday.
Home Secretary Jacqui Smith will make a statement on the situation in the Commons on Monday.
Merseyside Police have been searching two addresses in the Liverpool area.
Staffordshire Police said its officers have been searching an address in Newcastle-under-Lyme with the West Midlands Counter Terrorism Unit and Met personnel.
One of the suspects held at Glasgow Airport suffered severe burns and was taken to Royal Alexandra Hospital, in Paisley, where he remains in a critical condition. There is an armed police guard around the suspect.
Controlled explosion
The BBC has learned those arrested are believed to be of varying Middle Eastern nationalities.
A controlled explosion was later carried out at the hospital on a car, thought to be connected to the attack on Glasgow Airport, police said.
Searches have taken place at addresses in Houston, Renfrewshire, close to the airport.
The UK moved to its highest level of terror alert after the Jeep Cherokee crashed into the main doors of Glasgow Airport's main terminal and burst into flames.
The incident came the day after two Mercedes containing petrol, gas cylinders and nails were found outside the Tiger Tiger club in London's Haymarket and a nearby street on Friday.
Their devices did not detonate.
Their devices did not detonate.
Glasgow Airport was fully opened on Sunday afternoon, almost 24 hours after the incident.
Security has been stepped up across the country.
A number of other airports have stepped up security, including Heathrow, Edinburgh, Newcastle, Birmingham, Manchester and Blackpool.
A number of airports have taken extra measures, including Heathrow, Edinburgh, Newcastle, Birmingham, Manchester and Blackpool.
Heathrow's terminal was closed for a period on Sunday after a suspect package was declared safe.
Heathrow's terminal was closed for a period on Sunday after a suspect package was declared safe.
There was heightened security and a heavy police presence at Wembley Stadium, in London, where up to 63,000 people have been attending the memorial concert for Diana, Princess of Wales.
There was heightened security and a heavy police presence at Wembley Stadium, in London, where up to 63,000 people attended the memorial concert for Diana, Princess of Wales.
Houses were searched at Houston, Renfrewshire
Security is also to be stepped up at the Wimbledon Championships, in south-west London, when the tennis tournament resumes on Monday.
Security is also to be stepped up at the Wimbledon Championships, in south-west London, when the tennis tournament resumes on Monday.
Road blocks have been set up in front of the gates to the All England Club.
Road blocks have been set up in front of the gates to the All England Club.
'Al-Qaeda link'
Deputy Chief Constable Andy Trotter said British Transport Police would "do everything we possibly can to make people safe in their journeys to work tomorrow across the country".
Deputy Chief Constable Andy Trotter said British Transport Police would "do everything we possibly can to make people safe in their journeys to work tomorrow across the country".
Houses were searched at Houston, Renfrewshire
"We'll be out in force. We'll be doing a lot of things they can see and an awful lot of things they can't see in the background to make their arrival back at work on Monday morning as safe as possible," he said.
"We'll be out in force. We'll be doing a lot of things they can see and an awful lot of things they can't see in the background to make their arrival back at work on Monday morning as safe as possible," he said.
The prime minister told Andrew Marr on BBC One's Sunday AM it was "clear that we are dealing, in general terms, with people who are associated with al-Qaeda".
Home Secretary Jacqui Smith will make a statement on the situation in the Commons on Monday.
"It's obvious that we have a group of people - not just in this country, but round the world - who're prepared at any time to inflict what they want to be maximum damage on civilians, irrespective of the religion of these people who are killed or maimed," Mr Brown said.
Police have urged anyone with information to phone the confidential Anti-Terrorism hotline number on 0800789321.
Police have urged anyone with information to phone the confidential Anti-Terrorism hotline number on 0800789321.
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