Six people including a former police community support officer and a white Muslim convert were arrested in a series of raids yesterday in connection with a suspected terrorist plot against potential targets in Britain.
Three brothers, aged 18, 24 and 26, were arrested about a mile from the main Olympics site in east London but police said the planned operation was not linked to the Games or the Paralympics.
Two other men and a woman were arrested in west London. According to reports one of the men was a white Muslim convert who has appeared in a YouTube video railing against Britain's role in Afghanistan and the Royal family. Last year the same man named in reports appeared on a BBC documentary called My Brother the Islamist.
Police declined to give details on any suspected targets before the intelligence-led operation yesterday but said that an attack was not imminent.
The 24-year-old was shot with a Taser at Abbey Road, Stratford, by the Metropolitan police counter-terror command but did not need any hospital treatment, Scotland Yard said.
One of the brothers had been a police community support officer (PCSO) for more than two years until he resigned in September 2009.
"He was not deployed in a specialist or sensitive role," said a Scotland Yard spokeswoman. PCSOs do not have the full powers of warranted police officers but are often used for high-visibility patrolling.
Neighbours said the family had been living there for more than a year, and that people frequently came and went from the house wearing Muslim clothing. A blue police tent covered the door of the house yesterday.
Stephen Maguire, 23, who witnessed the operation from his bedroom overlooking the front of the house, said: "I heard the biggest bang ever and I saw a massive cloud of smoke and torches going up at the windows," he said. "It sounded like they were gunshots but they weren't."
Another eyewitness to the Stratford raid, Mark Window, told the BBC he had been woken up by an explosion just after 4am. "I looked out my window, saw loads of mini-explosions going off still, loads of black-clad figures milling around," he said.
"One was halfway up a ladder, through a window, and you realise it's some sort of police operation going on instead of kids messing about with fireworks which is what you think when you first wake up."
Another local in Stratford , who asked not to be named, described the men as "good people".
"They are religious and they go to the mosque," she said. "They are usual Muslim young boys."
The 29-year-old man, was arrested in a street in Ealing, west London, and another man, aged 21, and a woman of 30 were arrested at homes nearby.
Searches under the Terrorism Act were being carried out at eight homes around the city and at a business premise in east London. Scotland Yard declined to state the nature of the business. All those arrested were being questioned at a police station in southeast London.
The arrests come after Jonathan Evans, the director general of the Security Service, warned last month that Britain had faced a "credible terrorist attack plot about once a year since 9/11".
"In back rooms and in cars and on the streets of this country there is no shortage of individuals talking about wanting to mount terrorist attacks here," he added. "The threat is real and remains with us today."
The threat to the UK from international terrorism is currently rated substantial – the third highest of five levels. The rating is set by the Joint Terrorism Analysis Centre.