THE morning after the day which shook the world to its core and the long, grim search for signs of hope begins amid the ruins of a shattered nation.

Twenty-four hours earlier, the 110-storey World Trade Centre had been the workplace of 50,000 people and a towering symbol of wealth and power.

Now, all that is left is a vast, twisted wasteland of dust and rubble which heroic rescuers must comb for hidden survivors of history's most evil act of terrorism.

Thousands are dead, with Downing Street warning last night that hundreds of Britons may be among the victims.

The tireless search for answers was also gaining momentum last night. Police named two men they believe were involved in the twin terror attacks on New York and Washington.

One, Mohamed Atta, and the other, known only as Marwan, were named by the FBI. Their home was searched but it was not known if anyone was taken into custody.

The FBI also said it was investigating whether five Arab men, one a trained pilot, whose names were on passenger lists for the two flights hijacked in Boston, were the perpetrators of the attack on the World Trade Centre.

A third plane, hijacked after taking off from Washington, smashed into the Pentagon, and a fourth crashed south of Pittsburgh. It was seized after it took off from Newark Airport, near New York.

In Florida yesterday, an unknown number of people were taken into custody and interviewed.

In Boston, heavily-armed police searched an empty hotel room and found information linked to the possible perpetrators of the attacks.

The five Arab men were identified after a hired car taken from a car parking area at Boston Logan Airport was found to have an Arabic flight training manual and a copy of the Koran.

Two of the men, including the trained pilot, were brothers with passports while one man was traced to the United Arab Emirates.

And at the airport, FBI agents combed seats for DNA evidence and removed six bags of possible evidence for forensic examination.

In Maine, another car was seized in Portland where two suspected terrorists had boarded a flight to Boston before taking the hijacked flight. They were reported to have arrived from Canada shortly beforehand.

The police action came as the US Justice Department confirmed it believed the hijackers included trained pilots.

Spokeswoman Mindy Tucker said information gathered from the flurry of last-minute phonecalls from the doomed flights had pointed to three to five terrorists being on each of the planes.

Efforts were under way to establish if the terrorists were linked to a band of supporters in Canada of Osama bin Laden, the terrorist mastermind who is the number one suspect for the attacks.

Earlier, US Secretary of State Colin Powell, who led allied troops in the Gulf conflict, said: "It's a war not just against the United States, it's a war against civilisation." But despite mounting speculation that bin Laden was behind the bloodiest terrorist atrocity in history, there was no identifiable enemy target for America's wrath.

He spoke as rescuers fought a battle of their own in the rubble of lower Manhattan to save the lives of those still buried alive after the destruction of the World Trade Centre.

Secretary of State Powell vowed: "We will go after them. We will not let up."

He said of the American people: "We are at war and they want a comprehensive response. They want us to act as if we are at war and we're going to do that diplomatically and militarily."

But he said Washington was "far from selecting any particular military targets" for retaliation.

In Britain, Prime Minister Tony Blair said he was recalling Parliament for an emergency session tomorrow to discuss the crisis.

Across the globe there were fears of further attacks, of the damage that could be done to the world economy, and of the many long-term implications of a new and terrifying form of terrorism for which the US was defenceless.

But for thousands of families there was the terrible dread for loved ones who went to work or boarded planes yesterday and have not been heard of since.

Irishman Ronnie Clifford counted himself lucky when he escaped from the building, only to discover that his sister Ruth Clifford McCourt, 45, and her four-year-old daughter Juliana were on board the second jet to strike the towers.

Chilling accounts emerged of passengers on the doomed jets making final calls to their loved ones just seconds before they died - and evidence that some facing death went down fighting.

Flight attendant CeeCee Lyles called her husband at home in Fort Myers, Florida, on her mobile phone, said her aunt, Mareya Schneider.

"She called him and let him know how much she loved him and the boys," Ms Schneider said.

People screamed in the background, as Ms Lyles said "we've been hijacked" and the phone went dead.

Moments before his plane went down, businessman Thomas Burnett of California, called his wife, telling her he feared the flight was doomed.

Burnett, 38, told his wife: "I know we're all going to die - there's three of us who are going to do something about it."

* Palestinian leader Yasser Arafat yesterday donated blood for the victims of the US terror outrage and condemned "this horrible attack".

Asked if he had a message for the US people, Arafat said: "God bless you."