Extremists "with large agendas and little money can use rudimentary weapons" to sow terror, raising the spectre that the Mumbai attacks could embolden terrorists seeking to attack US cities, the top US investigation agency FBI warned.
The Federal Bureau of Investigation (FBI) is expanding its focus beyond Al Qaeda and into splinter groups, radicals who try to enter the country through the visa waiver programme and "home-grown terrorists," FBI Director Robert S Mueller said at the Council on Foreign Relations in Washington on Monday.
"The universe of crime and terrorism stretches out infinitely before us, and we too are working to find what we believe to be out there but cannot always see," said the head of the agency charged with protecting the US against domestic and international terrorism.
"Our primary threat continues to come from the tribal areas of Pakistan and Afghanistan," Mueller said. "But we are seeing persistent activity elsewhere, from the Maghreb and the Sahel to Yemen."
US, he said was increasingly concerned with pockets of people around the world that identify with Al Qaeda and its ideology. "Some may have little or no actual contact with Al Qaeda. Yet fringe organizations can quickly gain broader aspirations and appeal."
Citing a planned attack against Fort Dix, he noted the men FBI convicted had engaged in target practice in the woods of Pennsylvania. They had watched Al Qaeda training videos. They had a map of the base and a plan to get in. And they had purchased semi-automatic weapons from an FBI sting operation.
"Like the Mumbai attackers, these men wanted to inflict as much damage as they could. And as the Mumbai attacks illustrate, the simplest of weapons can be quite deadly when combined with capability and intent," Mueller said.
One particular concern, the FBI director said, springs from the country's background as a "nation of immigrants." Federal officials worry about pockets of possible radicals among melting-pot communities in the United States such as Seattle, San Diego, Miami or New York.
A Joint Terrorism Task Force led by the FBI, for instance, continues to investigate a group in Minneapolis after one young man last fall flew to Somalia and became what authorities believe to be the first US citizen to carry out a suicide bombing.
"The prospect of young men, indoctrinated and radicalised in their own communities . . . is a perversion of the immigrant story," Mueller said.