'They never made any noise, and there was certainly never anything suspicious'

It was an apparently normal day in Blackburn when two Asian men driving a gold-coloured Mercedes were brought to a dramatic and sudden stop. In what would become part of one of Britain's biggest anti-terrorist operations, a police car blocked the Mercedes from the front, while a second boxed it in from the side. Armed officers then forced the suspects out of the vehicle and on to the gutter.

It was an apparently normal day in Blackburn when two Asian men driving a gold-coloured Mercedes were brought to a dramatic and sudden stop. In what would become part of one of Britain's biggest anti-terrorist operations, a police car blocked the Mercedes from the front, while a second boxed it in from the side. Armed officers then forced the suspects out of the vehicle and on to the gutter.

At gunpoint they were ordered to put on white protective boiler suits to prevent any forensic evidence from them being contaminated or lost. They were then driven away. This high- profile arrest on Tuesday afternoon was repeated in raids throughout London, Luton and Watford, in which 13 men in their twenties and thirties were arrested.

The operation was the culmination of weeks of surveillance work triggered by an investigation by MI5 into a suspected al-Qa'ida cell.

Tincie Hill, 27, yesterday described what happened in the Blackburn incident. "Both of the men in the car were Asian," she said. "The passenger was laid in the gutter with two policemen with guns trained on him. The driver was on his knees at the back of the car with guns pointing at him as well.

"The police had put the men in white suits and had put bags over their hands and feet."

Ruth Lazell, 40, saw the incident unfold outside her front gate. She said: "There were armed police officers telling us to go back inside the house, about 15 or 20 of them in all. They had their guns pointing at two Asian lads who were on the floor outside the car."

A similar pattern to the Blackburn arrest emerged throughout Tuesday, provoking unrest among Muslim leaders who say that their community is increasingly feeling persecuted by the authorities in their ongoing anti-terrorism activities and investigations.

In Luton, witnesses said an Asian man was pulled from his car by seven armed police officers. The suspect was driving along the A6 Bedford road and was stopped when he pulled into a side street.

Leigh Mayes, 70, who watched the operation from the window of his house, said that seven officers carrying semi-automatic machine guns held the man against his maroon hatchback for nearly three hours while forensic teams carried out their searches.

"They just stood there in the blazing sunshine and also throughout the heavy thunderstorm," he said.

Roger Walker, who lives next door to a house in Bushey, Hertfordshire, which was also raided, described how there were "police cars and policemen all over the place".

He said that an Indian couple, in their fifties, lived at the house with their son, who he thought was in his early twenties. Their daughter, who was also in her twenties, had married and moved out two weeks ago, he said.

Mr Walker added: "I know the family to speak to and they have always been very friendly. Quite often people would be coming and going from the house, but they never made any noise and there was certainly nothing to suggest anything suspicious.

"About three years ago, the daughter became very religious and soon after the son did too."

As usual, the terrorist suspects were taken to the high-security police station in Paddington Green in central London for questioning. Within hours one of the men - who had been arrested in Willesden, north London - was released without charge.

Police officers are continuing their investigations in London, Luton and Blackburn.