"For all we know there could be 50 more bombs stored in a garage somewhere, just waiting to be planted," one Scotland Yard source said yesterday.
The orthodox Jewish population of Stamford Hill, north London, has been on a state of high alert all week amid concern that as one of the country's best-known Jewish communities it could be the next target.
"People are scared," said Loz Meyer, 19, who works at the kosher Moses supermarket. "The young people more than the old ones. The old ones say 'we beat the Nazis once, we will beat them again'. But the young people are terrified. My 21-year-old friend told me she felt she was too young too die."
The 50-odd synagogues in north London have tightened security after last week's Brick Lane bomb. Religious restrictions on using technological equipment such as mobile telephones during the sabbath - Saturday - have been lifted so people can act promptly.
"We discourage panic. We encourage people to carry on as normal and keep their eyes and their ears open. The key is vigilance," said Joe Lobenstein, mayor of Hackney and vice-president of the Orthodox Hebrew Congregation. He has been meeting police all week to discuss community security. There were some 40 bomb scares in Hackney last week.
The picture is similar in Southall, west London, home to one of the largest Asian communities in the UK. Kultar Kapoor, 34, owner of a roadside stall in the Broadway, migrated to the UK from Afghanistan three years ago to escape the Taliban. "Those old feelings of fear and apprehension which haunted us in Kabul have been revived over the past week. Now, I worry constantly about my children, and my wife."
Volunteers recruited by the anti-racist Southall Monitoring Group were planning to patrol the streets, but the move has been criticised by some. "These efforts could divert the police's attention from the real issue - the activities of right-wing groups. The police force does not have the complete trust of the Asian community at the moment. It would be better to build a genuine partnership to tackle this problem," said Virendra Sharma, a local councillor.
Mohammed Iqbal, 35, runs a discount shop in Ladypool Street in Sparkbrook, one of Birmingham's oldest Asian communities. "Are we worried? It's all we've been talking about."
At the police station, Sergeant Steven Bruton said: "We're trying to reassure and emphasise that we need to work together to be more vigilant. I haven't noticed any tension or anxiety."
Locals disagree. They want to see an increase in security, in particular closed circuit television. Mainly, though, they talk about how depressing it is that after living here for many years, they still feel persecuted. "When I was a taxi driver the verbal abuse was common," said Iqbal. Restaurant owner Hussain Saghir, 30, described a recent incident when five men carrying baseball bats drove a van around throwing eggs at people. "That's quite rare. But what can you do except hope it will go away? With these bombs you worry there's more widespread support."
There are also concerns that neo-Nazi activity has increased under Labour with the far right feeling more alienated. "When Labour was in power last we had the skinheads and National Front marches," said Mohammed, a Kashmiri in his sixties.
Even so, many people believe the bombings will serve to stren-gthen anti-racist feelings in the country's multicultural areas, triggered by the murder of black teenager Stephen Lawrence.
"We believe we're on the crest of an anti-racist wave. If something was to happen it would only increase the anti-racist feeling in Bradford," said Ateeq Siddique, of the Bradford Com- mission for Racial Equality.