More people died in terrorist attacks last year than in any other year in history, according to a report by the United States Government.

The report - the latest edition of the annual State Department reports - says 3,547 people were killed in 2001 world-wide - the overwhelming majority of them in the attacks in the US on 11 September.

The report comes just as Americans are receiving new warnings that further civilian attacks are likely.

There will be another terrorist attack, we will not be able to stop it

Robert Mueller, FBI chief

The head of the FBI, Robert Mueller, says he believes it is inevitable that suicide bombers will eventually begin attacks in the US, as they have in Israel.

His comments came only a day after the Vice-President, Dick Cheney, said further attacks on the US by Osama Bin Laden's al-Qaeda network were almost certainly on their way.

International tragedy

The State Department report states that people from 78 countries around the world perished in the World Trade Center disaster.

It says the chief success so far in the campaign against terrorism was the overthrow of Afghanistan's Taleban regime.

The report's publication comes as senior US officials continue to warn about the increasing likelihood of another attack on American soil.

Cheney: Not a matter of if but when

The latest is from the FBI Director, Robert Muller, who told an audience in Virginia: "There will be another terrorist attack, we will not be able to stop it."

He said he wished he could be more optimistic but he felt that suicide attacks on public places would come eventually.

Earlier, Mr Cheney had said that it was "not a matter of if, but when" the militants blamed for 11 September would strike again.

The chairman of the Senate Intelligence Committee said that other extremist groups as well as al-Qaeda may be involved.

Senator Bob Graham told American news channel NBC that the country's enemy "is not al-Qaeda alone", and mentioned several prominent groups considered by the US to be terroritst organisations - including Hezbollah and Islamic Jihad - that had the capacity, and the desire, to attack the US.

He said he believed a number of extremists had come into the US in the last few months, hidden in container ships.

'Chatter in the system'

Such remarks from prominent members of the US intelligence community are an indication of increasing gloom within the American intelligence community, already under fire for failing to spot - and possibly prevent - the 11 September attacks.

National Security Adviser Condoleezza Rice said on Sunday that the US was on a far higher state of terror alert now than it before the attacks.

Bush is embroiled in a row over intelligence reports

Intelligence specialists have said there has been an increase in the volume of messages between al-Qaeda cells, similar to that noted before 11 September.

A senior Bush administration official quoted by the New York Times suggested that the new intelligence reports had yet to form a coherent picture.

"There's just a lot of chatter in the system again," the official said.

But a recent suicide bombing in Karachi, Pakistan, and an attack on a synagogue in Tunisia are seen as evidence by US intelligence officials that al-Qaeda still has the potential to stage deadly attacks.