AT least one hundred British citizens have been killed in the US terror attack, Foreign Secretary Jack Straw officially announced today.

And he said the UK death toll could eventually reach the "middle hundreds".

The Blackburn MP said he understood that up to 100 Britons killed in the attacks on the World Trade Centre and Pentagon had already been identified and that Scotland Yard's casualty bureau was in the process of contacting the families of the dead.

Speaking from the Foreign Office, Mr Straw said British forces were in a state of readiness but said he did not wish to discuss what action might be taken in response to the attacks which have shaken the world.

Eighty two bodies have so far been recovered from the ruins of the World Trade Centre, according to figures released by the mayor.

Rudolph Giuliani said only five people had been pulled alive from the rubble by rescue teams since the horrific attack on Tuesday.

Officials estimate the final death toll could be 20,000 with 10,000 of those thought to be in a shopping mall in the centre.

As the smouldering ashes of New York's World Trade Centre slowly yielded unimaginable carnage, investigators fanned out across the country to track the conspirators who orchestrated an unprecedented day of terror from the air.

In one indication of the potential death toll, Mayor Rudolph Giuliani said that the city has requested 6,000 body bags from federal officials. Mr Straw said British intelligence services would continue to work with the US authorities in sharing information about the attacks, but said it would never be possible to gather intelligence on "every evil group in the world."

Asked when trans-Atlantic flights would be able to resume he said US security and the safety of flight passengers were the over-riding concerns.

"This was far from mindless, this was completely calculated terrorism by wholly perverted people, but people who showed that they were capable of planning at a very high level and executing their plans," he said.

Mr Straw later said the international rule of law might need to be changed after the attacks in America.

"It's very difficult to extradite people from one country to another because we use 19th century rules in a 21st century situation," he said.

"This was absolutely calculated, a calculated attack on democracy, on civilisation."

Mr Straw denied that the British Government was trying to persuade the Americans to "cool" their response.

There should be, he said, "a determined response, a response that is based on judgments, and of course which is based on evidence".

Countries which had harboured terrorists should be made to face a "stark choice" if they were to enjoy the benefits of being part of the international community.

Mr Straw declined to say whether the British Government believed Osama bin Laden was behind the attack.

"We, as the United States have been, have been very careful not to engage in the public speculation," he said.

"The people in the United States are shocked, they are in grief, they are angry, but from my conversation yesterday with Secretary of State Colin Powell, it is also entirely clear that they are determined to ensure ... that those responsible directly and indirectly, are held accountable for these acts and by God, so they should be."

The perpetrators should be prevented from ever being able to carry out another attack.

The Foreign Secretary cited the decision by the UN Security Council which said the perpetrators of the attack and anyone who was harbouring them would be held to account.

"We now have the whole of the international community determined to take action both to deal with this threat and also if it is humanly possible to deter and to reduce the risks of such threats happening again."