Warning such attacks could be viewed by terrorists as a possible way of proceeding in the future, Federal Bureau of Investigation Director Robert Muller said, "Intelligence and other security agencies would have to reinvigorate efforts to make certain that we've done everything we can to prevent such type of attacks."

Delivering a speech on 'Global Terrorism [Images]: The FBI's Role', Muller said the Mumbai attack, which killed more than 170 people and wounded over 300 was an attack both highly co-ordinated and deceptively simple in its execution.

Muller, who took over the FBI just days before 9/11, said, "The Mumbai attack had displayed that the terrorists with large agendas and little money can use rudimentary weapons to maximise their impact."

"It again raises the question of whether a similar attack could happen in Seattle, San Diego, Miami [Images] or Manhattan," he said.

Muller said although the Al Qaeda [Images] remains a threat to the US and worldwide, security planners must also focus on less well known terrorists groups as well as home-grown terrorists.

The FBI chief warned, "Terrorists could be merely e-tickets away from the US".

The US, Muller said, is concerned with people and groups around the world that identified with the Al Qaeda and its ideology. He said Mumbai attacks had brought to the fore the need for better co-ordination and co-operation among intelligence and security agencies of major countries like US, India, Pakistan, United Kingdom and others.