En route to school or work, many New Yorkers paused at impromptu shrines that have sprung up around the city. Some of the shrines are elegant in their simplicity. In Washington Square, flowers were woven through the links in a chain fence; alongside them are posted simple notes expressing personal sadness - not anger - or gratitude to New York's police officers and firefighters. Hundreds of candles have been placed on the pavement below.

Other shrines are more poignant in their despair. Outside a New School University facility on 11th Street in Greenwich Village that is serving as the information centre for St Vincent's, the hospital closest to the blast site, dozens of missing-person notices have been posted on police barricades.

The faces in the pictures of the missing are of all colours, with surnames of varied origin, including Chinese, Hispanic, Indian, Jewish, Korean and Russian. All the missing - barring a miracle or two - are dead. But in one rare note of 'optimism' which says much about the scale of this tragedy, New York Mayor Rudolf Giuliani estimated on Thursday that about 4,700 people are still missing.

It now looks as if the overall death toll, including those who died at the Pentagon - also hit by an airliner - and on the hijacked planes, will exceed 5,000. That would be more than double the 2,400 Americans who died during the Japanese attack on Pearl Harbour on December 7, 1941, but far below initial fears that tens of thousands of people might have been killed in New York alone.

At peak business hours, as many as 50,000 people worked in or were passing through the World Trade Centre, which in addition to the twin towers, includes many subsidiary office towers that also have collapsed.

So, as bad as the timing of the attack was and as high as the death toll will be, both could have been much worse.

As soon as the north tower was hit at 8:45am on Tuesday, people were prevented from entering both towers and an evacuation began. Workers in the south tower had a precious 18 minutes before it was hit by the second plane.

And with another 57 minutes before the south tower collapsed and 86 minutes before the north tower collapsed, thousands of people were able to make it out.

Had the attack occurred either mid-morning or mid-afternoon, the United States could have lost tens of thousands of people in the space of an hour or two. By way of comparison, 58,000 Americans died in the Vietnam War.

I was at my mother's home on the North Shore of Massachusetts when my father, who was listening to radio reports while driving to work, called in the news.

As a current-affairs junkie from an early age and now a journalist, I have always loved major news events. The bigger they are, I long believed, the more exciting.

But this time, for the first time that I can remember, there was numbness rather than excitement, especially after it emerged that the two flights which ended in the World Trade Centre originated at Logan International Airport in Boston.

Suddenly, getting back to work at this newspaper's Guangzhou bureau - I had been scheduled to fly out of Logan on Wednesday morning - seemed less important.

Like most Americans, I mentally totted up friends and family members working in New York, especially in the financial district. Then, in stunned disbelief, I sat to watch the tragic events unfold on television.

Reconciling the news with the spectacular late-summer day that was dawning over Boston was impossible. The picture-perfect weather lent the events a bizarre quality, as if it was just a Hollywood movie.

I set out for New York a day later, on Wednesday afternoon. Boston is only a 45-minute flight from New York, but with all airports closed, the next best option was a four-hour train ride.

As the train made its way along the southern coast of New England, American flags along the route flew at half-mast. The skies above, usually a busy air corridor, were empty except for two military helicopters over Connecticut.

I arrived in New York as night fell. The scene could not have offered a more surreal contrast to the made-for-television footage that had dominated network broadcasts a day earlier.

In the gathering darkness, a massive and stubborn cloud of smoke and dust, exacerbated by yet another building collapse, drifted into the night air where the twin towers had stood.

Exiting Penn Station, I was immediately struck by the stench of fires still burning at the blast site. Southwards near police lines, the stench grew stronger and the number of people wearing cloth masks increased. The smoke and dust became so thick that, from just a few blocks north of the site, the massive pile of rubble could only be glimpsed intermittently.

It seemed impossible that less than 12 hours later, another glorious day would dawn and school children and commuters would begin to resume normal routines.

In times of national crisis, Americans have a tendency to wrap themselves in the flag and tie yellow ribbons around trees with an enthusiasm that strikes many foreigners as corny.

Indeed, after tragedy struck on Tuesday morning, radio stations 'honoured America' by playing the national anthem every hour.

Members of the House of Representatives and Senate gathered on the steps of the US Capitol building, began to sing a reportedly spontaneous rendition of America the Beautiful.

But it would be a mistake to equate such sentimentality with weakness. An icy resolve underlies the seemingly over-the-top displays of American patriotism. Hell hath no fury like the United States of America when it has been damaged as suddenly, deeply and unexpectedly as it was on Tuesday. It is a rare and amazing experience to watch an angry and powerful nation steel itself for war. It last happened in the US after the attack on Pearl Harbour.

The Government has not yet said against whom this war will be waged, but President George W. Bush has pledged not to distinguish between the terrorists who carried out the attacks and the nations that harboured them.

The war might also come to resemble a Hollywood production, but like the opening salvo fired on Tuesday, it is going to be all too real.