"Thousands of lives were suddenly ended by evil, despicable acts of terror," Mr Bush told the nation on television.

The World Trade Center in New York was destroyed and the Pentagon in Washington seriously damaged when hijacked airliners slammed into them on Tuesday.


People fled screaming

"Today our way of life, our very freedom came under attack in a series of deliberate and deadly terrorist acts," Mr Bush said.

He warned the US would make "no distinction between the terrorists who committed the attacks and those who harbour them".

Hunt

The full resources of the US intelligence community and law enforcement agencies were searching for those who organised the attacks, Mr Bush said. Thousands are feared to have died inside the buildings and about 260 more are presumed to have perished on board the planes.

US officials voiced suspicions that the Saudi dissident and Islamic militant Osama bin Laden - who is based in Afghanistan - may have been responsible for the attacks.

New York remains in a state of intense fear and confusion, made worse by a thick fog of ash, fumes and debris from the ruins of the World Trade Center. Huge explosions rocked the Trade Center as horrified onlookers watched two passenger jets plunge into its towers.

Panicking office workers jumped from windows in the skyscraper as it collapsed during attempts to evacuate the building.

Another nearby building, Salomon Brothers 7, collapsed several hours after the original catastrophe.

Mr Bush said the pictures of the attacks "filled us with disbelief, terrible sadness and a quiet, unyielding anger" "These acts were intended to frighten us, but they have failed. Terrorist acts can shake the foundations or our biggest buildings but cannot touch the foundation of America."

In a series of spectacular blows:

• Two hijacked passenger airliners plunge into the twin towers of the World Trade Center, the subsequent explosions and fires causing the buildings to collapse
• The Pentagon is partly destroyed by another hijacked plane which crashes into it shortly after the New York attacks, setting it ablaze
• Unexplained explosions are reported near the State Department and Congress buildings in Washington

Another hijacked passenger jet - a United Airlines 757 - crashes in Pennsylvania, south-east of Pittsburgh, with all 45 people on board feared dead.