By Mark Riley

SYDNEY, AUSTRALIA -- People are running out of the smoke in their dozens. Some are screaming. Most have eerily blank expressions. Looks of absolute disbelief. They are covered in ash. They hold handkerchiefs over their mouths to filter out the choking smoke."

This can't be happening, this can't be happening," one man is saying, over and over. He is slapping his leg. A slap for every word. Harder and harder. "This can't be happening!"

Alan Hess, standing nearby, says: "It is surreal. It is like watching a movie. A horrifying, real-life movie."

The skyline of the city no longer exists as it did. The twin towers that stood as sentinels at the bottom of Manhattan are now a mass of rubble, smoke and indescribable human tragedy.

No one seems to know how many people would have been in the buildings. It was surely thousands.

Thousands of lives lost. Thousands of families destroyed.

Thousands of childhood memories, histories, hopes and dreams, laying dead in the rubble of two towering buildings.

In that rubble, too, lays the once-reflexive feeling of security and strength that Americans held so passionately. It was a security held as inherent in the very structure of the world's greatest democracy - a security now shattered by the worst act of terrorism ever witnessed.

"Leave Manhattan if possible! Leave Manhattan if you can!" the police are yelling at the crowds on the streets.

People look around, wondering where they can go and how they can get there.

The city is clogged. Roads are blocked. The subways are closed. The bridges and tunnels on to and off Manhattan are closed.

The part of the sky that isn't clogged with plumes of black smoke is filled with aircraft.

Military jets zoom overhead. Helicopters have cut off the air space at either end of Manhattan Island. Wall Street is shut down. The financial markets are closed. Mobile phones do not work.

Schools are emptying children into the streets. They hold hands and look around them with expressions of innocence. They cry for their mothers.

Deliverymen slouch in the cabins of their vans, double-parked, triple-parked all around the city. Their radios are blaring with news of the attack.

"America is at war with terrorists," one announcer is screaming. "Our country is at war."

Mark Riley writes for the Australian Online Newspaper The Age