The US Federal Bureau of Investigation (FBI) has been given new powers to monitor the activities of people suspected of planning acts of politically motivated violence.

The Justice Department in Washington has issued new guidelines on domestic surveillance - the first for 25 years.

From now on, FBI agents will be able to spy on people, organisations and events without having to show evidence that a crime has been or is being committed.

The guideline changes ... are important steps to help remove unnecessary bureaucratic obstacles to the effective investigation of terrorist cases

Robert Mueller, FBI director

The new rules will apply only to what are perceived as counter-terrorist investigations, and will include internet surveillance.

The change, announced by Attorney General John Ashcroft, comes after the FBI's announcement of a major shift in focus from criminal investigation to terrorism prevention.

In recent weeks, the bureau has faced growing criticism for its failure to act on intelligence warnings prior to the 11 September attacks.

Safety v liberty

From now on, the mere suspicion of a person or group's involvement in terrorism will be enough for the FBI to begin surveillance.

The surveillance involved could mean going undercover at public events or simply collecting data on the internet.

The new FBI will focus primarily on preventing terror attacks

The old notion of probable cause, in which agents had to show evidence of some offence, will no longer apply.

Civil rights groups are concerned that the new rules might infringe people's rights.

The American Civil Liberties Union described the changes as the "latest power grab by an administration that seems determined to undermine the bedrock values of liberty, equality and government accountability".

But Justice Department officials say the guidelines are strictly focused on counter-terrorism work.

"The guideline changes ... are important steps to help remove unnecessary bureaucratic obstacles to the effective investigation of terrorist cases," said FBI director Robert Mueller.

This latest announcement comes just a day after Mr Mueller announced intensive restructuring within the FBI, following criticism of its operations in the run-up to 11 September.

The shake-up is one of the most far-reaching in the history of the bureau.

The revamped FBI is to take on an extra 1,600 agents and develop closer ties with its overseas counterpart, the Central Intelligence Agency (CIA).

John Ashcroft described the plans as "shifting the FBI's structure, culture and mission to one of preventing terrorism".

'Connecting the dots'

One of the main criticisms levelled against the FBI came from a field agent in Minneapolis who complained that FBI headquarters in Washington ignored information about Zacarias Moussaoui, who is alleged to have been involved in planning the 11 September attacks.

An FBI agent warned of terror suspect Zacarias Moussaoui

In her criticism, Coleen Rowley said that agents in Minneapolis unsuccessfully appealed for a search warrant for Mr Moussaoui's computer after he was arrested at a local flying school.

The FBI is also under fire for its failure to act on information from field agents in Phoenix, which might have given clues about the terror attacks on New York snd Washington.

Acknowledging the FBI's failure to make the connection, Mr Mueller said: "I can't say for sure that there wasn't the possibility that we would have come across some lead that would have led us to the hijackers.

"It is of critical importance that we have that connection of dots to prevent another attack."