RENEE MONTAGNE, host:

This is MORNING EDITION from NPR News. I'm Renee Montagne.

Britain today led Europe in two minutes of silence for the 53 people killed in last Thursday's attacks in London.

(Soundbite of bell tolling)

MONTAGNE: Only the bells of Big Ben broke the silence as London's Black Cabs pulled over, trains stopped, the queen stood still outside of Buckingham Palace. Last week's attacks are believed to mark the first suicide bombings in western Europe. We'll have more on that in a moment.

First, NPR's Ivan Watson is out on the streets of London. And, Ivan, how generally was this moment of silence, or moments, observed?

IVAN WATSON reporting:

Rene, here in--what you can hear is London's very busy Trafalgar Square. At noon local time, thousands of pedestrians, cars and red double-decker buses stopped in their tracks as the city, as the country, observed these moments of silence to remember the victims of last Thursday's terror attacks. London's mayor said the goal of this was to remember all those who died, and to show defiance to those who would seek to change the character of the city through terror. And there were a gathering of emergency services, of representatives of the main religious communities here, they were all standing on the steps of the square's National Cathedral, in front of signs that said, `London United,' and, `One City, One World.' Later today, here in Trafalgar Square, the public will be invited to sign a book of condolences and a vigil service will be held here.

MONTAGNE: What are other countries doing as an observance?

WATSON: Well, the rest of the European Union has also been urged to participate in this moment of silence. We've heard that the governor of New York has announced that the states affected by the September 11th attacks--Virginia, New York and Pennsylvania--that they will try to remember London's attacks, as well as Bali and Madrid, also targets of past terrorist attacks.

MONTAGNE: Ivan, talk to us about the investigation itself. What are the latest developments there?

WATSON: Well, last night police raided a location in Aylesbury. That's a town about 40 miles northwest of here. They say they're continuing the interrogation of a 29-year-old male who was arrested earlier this week in a series of raids in the northern English town of Leeds. In addition to the four chief suspects, whose movements are being investigated right now, in the week leading up to the terror attacks, and who are believed to have been killed in those explosions, police are hunting for a fifth man, a possible mastermind. Britain's security chief, the homeland secretary, Charles Clarke, he suggested that the first four suspects, that they're only foot soldiers, and only one element of a larger organization.

MONTAGNE: And in the middle of all of this, the country is dealing with the fact that, it's settling in, the four suspected bombers are British citizens.

WATSON: Right, the police haven't formally identified the four suspects, but the press here has published extensive details on three of the four men, indicating that they are of Pakistani origin, that they're born here in Britain from that northern city of Leeds. They published their birth certificates. They're an 18-year-old man, a 22-year-old man, another in his 30s, a teaching assistant to the local school. And this is a chilling notion. People are asking `What could have compelled these people to possibly become suicide bombers who would kill other ordinary citizens, civilians, around them?'

This has put the Muslim associations here in Britain on the defensive. Representatives of the 1.6 million Muslims in this country, roughly 3 percent of the population, they are saying that these men, if they were, in fact, suicide bombers, that they are criminals, that this was an un-Islamic act, that this does not represent the religion as a whole. And British leaders have said that we should not stigmatize any one community for the acts of a few and yet all people are looking towards these communities and asking `Could anybody have done something more to prevent these people from possibly becoming radicalized, from choosing to attack their own country?'

MONTAGNE: Ivan, thanks very much.

WATSON: You're welcome, Renee.

MONTAGNE: NPR's Ivan Watson in Trafalgar Square, London. Transcript provided by NPR, Copyright NPR.