The attack forced the first mandatory evacuation of the U.S. Capitol and drove congressional leaders into safe but secret locations. The assault involved the hijacking of four commercial planes and brought normal life across the country to a standstill, turning major cities into eerie ghost towns.

All financial markets were closed and millions of workers were sent home early. All commercial flights were canceled and, in a move unprecedented in American history, all airports were shut down. For the first time since D-Day, major league baseball games were canceled.

No group took immediate responsibility for the attack, but suspicions centered on an implacable U.S. foe - exiled Saudi Osama bin Laden, whose followers were held responsible for murderous attacks on U.S. embassies in Africa.

The entire nation was brought to a halt by scenes of terrified people fleeing the mayhem flashing across TV screens. The mighty twin towers, anchoring the southern tip of Manhattan imploded one at a time, sending a massive plume of dust and smoke billowing over the city.

"Horrific" Number Of Fatalities" New York Mayor Rudolph Giuliani said the death toll could ultimately be "horrific" and that the city's hospitals were swamped with casualties. Hundreds of firefighters and police are missing and feared dead after trying to rescue others. Officials feared the death toll could climb into the thousands - perhaps tens of thousands - as 40,000 people alone worked in the steel and glass Trade Center towers and a nearby 47-story building, World Trade Center No. 7, which collapsed seven hours later after a raging fire. World leaders condemned the attacks and offered to assist in the massive relief effort now underway in southern Manhattan. German Chancellor Gerhard Schroeder called the strikes a "declaration of war against the civilized world." Israeli Prime Minister Ariel Sharon echoed Schroeder's condemnation of the attacks and extended "deepest condolences and heartfelt sympathy to the American people…following the terror attacks against the US...All Israelis stand as one with the American people. Our hearts are with you, and we are ready to provide any assistance at any time."

Late-Breaking Developments

Explosions lit up the night sky in Kabul, Afghanistan, the nation where bin Laden is believed to live, and reports said there were missiles flying across the city. A senior Pentagon official denied U.S. involvement and responsibility for the attack was laid at the feet of an Afghan opposition group.

Late Tuesday night, 1010 Wins radio in New York reported that two men were arrested en route to the George Washington Bridge, driving a van packed with "enough explosives to level the Bridge and anything on it." Police officials declined to comment on the identity or nationality of the men and later denied that the van contained any explosives.

Media agencies reported that, unbelievably, survivors were still being pulled out of the rubble beneath the World Trade Center wreckage and that furious relief efforts would continue through the night and for the foreseeable future. Reportedly, two survivors, still buried beneath the rubble, have contacted relatives in Seattle via cellular phone and informed them of their exact location and the location of other survivors.

All citizens - except residents and licensed emergency workers - are warned, on threat of arrest, to stay clear of Manhattan south of 14th Street.

Early Wednesday morning, a report in The Boston Herald alleged that authorities in Massachusetts have identified five Arab men as suspects in Tuesday's attack on New York City and seized a rental car containing Arabic-language flight training manuals at Logan International Airport.

Two of the men were brothers whose passports were traced to the United Arab Emirates, the unidentified source told the Herald. One of the men was a trained pilot, the paper reported on its Web site on Wednesday.

The paper said investigators suspect the two brothers were aboard hijacked United Airlines flight 175, which pilot union officials said was one of the aircraft that crashed into the World Trade Center.

The Nation Reacts

The attacks presented President Bush with the toughest test of his eight-month presidency. He cut short a trip to Florida and flew to Offutt Air Force Base in Nebraska, after stopping briefly in Louisiana where he vowed to bring those responsible to justice.

Later, in a nationally televised address from the Oval Office, President Bush expressed his anguish over the attacks and vowed that the assaults would not go unanswered.

"Thousands of lives were suddenly ended by evil, despicable acts of terror," Bush said. "The sight of planes flying into buildings, fires burning, huge structures collapsing filled us with disbelief, terrible sadness and a quiet, unyielding anger. Our first priority is to get help to those who have been injured, and to take every precaution to protect our citizens at home and around the world from further attacks," Bush continued.

"Comparable To Pearl Harbor"

It was the worst attack on American soil since Japanese warplanes bombed the U.S. fleet at Pearl Harbor on Dec. 7, 1941, killing 2,280 soldiers and 68 civilians and forcing the United States into World War Two.

Former Secretary of State Henry Kissinger told CNN, "This is comparable to Pearl Harbor and we must have the same response and the people who did it must have the same end as the people who attacked Pearl Harbor."

Confusion And Mayhem

The attacks triggered scenes of panic, disbelief and heroism in the largest U.S. city, where police and firefighters risked their lives to save people from the Twin Towers before its 200,000 tons of steel frame and 43,000 windows came smashing down, covering lower Manhattan in a shower of soot, ash, and debris.

"I looked outside and saw a big chunk of the World Trade Center missing," said Verizon employee Ellen Leon. "Fifteen minutes later I saw people jumping out of the building. Bodies were flying out. I don't know if they were already dead or if they were just going to die."

"It's nuts, there is debris and dust everywhere, and it looks as though a volcano erupted down there," said Michael DeVita, who was working on the 84th floor of World Trade Center Building No. 2 when the first plane hit Building No. 1.

"Hundreds of people are burned from head to toe," said Dr. Steven Stern at St. Vincent's Hospital in the Greenwich Village neighborhood of lower Manhattan. Rescue workers used commuter ferries to carry victims across the Hudson River to safety in Hoboken, New Jersey, where the scene resembled a war zone, with victims laid out on stretchers, limping on crutches, and others walking without a shirt and with their pants torn.

At press time, government officials were urging all non-emergency personnel to stay out of the city. Reportedly, New York City Public Schools and the City University of New York will not open Wednesday. The president has declared New York a federal disaster area, and Governor Pataki has called in the National Guard.