BRITISH police issued a public warning overnight after the latest in a series of letter bombs took the number of people injured to seven in five days, fuelling fears of a concerted bombing campaign.
Both Prime Minister Tony Blair and Home Secretary John Reid voiced concern over the attacks - several of which have targeted motoring-related firms - after the latest incident left three people injured in south Wales.
"Naturally, these incidents are worrying ... It is important that we allow police to get on with their investigation without undue speculation," Mr Reid said, in his first comments on the blasts.
The Association of Chief Police Officers (ACPO) said there had been seven incidents in the last three weeks, and warned that the public must be prepared for the risk that there will be more.
"I am appealing today for companies, organisations and individuals to take extra care when handling mail," said Assistant Chief Constable Anton Setchell, ACPO's national coordinator for domestic extremism.
"The packages received so far have caused minor injuries, but could have been more serious," he said.
In the latest blast, three people were injured at the government's Driver and Vehicle Licensing Agency (DVLA) in Swansea, south Wales, police said.
Initially only one person was reported hurt.
That followed blasts on Tuesday in London, at a firm dealing with London's controversial congestion charge, and on Wednesday at a firm west of London which reportedly manages speeding fines. It also emerged that a previously-unreported device injured a householder in Folkestone, Kent, on Sunday.
Before that, there were three other incidents last month in Birmingham and Oxfordshire, Chief Constable Setchell said, adding that the name of a dead animal rights campaigner was found on one of the devices.
Police have made no formal link between the blasts, but the British press has speculated about the possibility of a disgruntled motorist targeting authorities who control the roads in Britain.
One well-known campaigner against speeding fines, the self-styled "Captain Gatso" of Motorists against Detection (MAD), said overnight he did not condone letter bombs, but understood drivers' anger.
He cited the case of councils charging hundreds of pounds for residents' parking permits, a situation particularly common in London.
"Before you've even turned the keys, they're hammering you in your vehicle," said Gatso, whose name comes from a common make of roadside speed camera.
"So something's got to give," he said, while adding that he "completely" condemned the bombings.
Britain has been on high alert since July 2005 suicide bombings which killed 56 people in London. There is no suggestion that the latest bombings - all of them relatively small - have any links with Islamic extremism.
Prime Minister Tony Blair, asked about the latest blast at his weekly question-and-answer session in Parliament, said: "We are looking and investigating very closely the incident concerned.
"Can I express my sympathy to all those people who have been caught up in those incidents," he said. "As soon as we have some news that we can properly give .. then we will do so."
Police chief Setchell said the devices were more like fireworks than bombs, designed to shock rather than to seriously maim or kill.
But he said police are nonetheless taking them very seriously.
"We have had no contact from any group or organisation claiming any responsibility or setting out their motivations," he said. "I want to keep a completely open mind about the motivations behind these packages."
