The United States has been rocked by devastating attacks on the World Trade Center in New York and the Pentagon in Washington. Massive casualties are feared, with thousands feared to have died inside the buildings, with hundreds more presumed to have perished on board the hijacked planes.

In a series of spectacular blows:

• Two hijacked passenger planes 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 airliner 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 passenger jet - a United Airlines jumbo 747 - has crashed in Pennsylvania, south-east of Pittsburgh. It is not clear whether that too had been hijacked.

President Bush cut short a visit to Florida, leaving on the presidential jet with a fighter escort.

"Make no mistake, the United States will hunt down and punish those responsible for these cowardly acts," he said after the plane landed at a Louisiana military air base.

White House officials would not give the plane's final destination.

The attacks have caused chaos on world stock markets. Trading has been suspended in New York while share prices on European exchanges plummeted.

International air travel has been severely disrupted.

New York panic

Huge explosions rocked the World Trade Center after horrified onlookers watched two American Airline passengers jets plunge into its towers.

Panicked office workers jumped from windows in the Center - which is visited by more than 150,000 people every day - as it collapsed during attempts to evacuate the building.

New York's Mayor, Rudolph Giuliani, said a "tremendous" number of lives had been lost in the city.

And Dr Steven Stern at St Vincent's Hospital in the Greenwich Village area of lower Manhattan said: "Hundreds of people are burned from head to toe."

Appeals have been issued for supplies of blood to help treat the injured.

American Airlines told BBC News Online that the two aircraft had a total of 156 passengers and crew on board - all are feared dead.

Pentagon collapse

 

In Washington, the Pentagon - the heart of the US military establishment - suffered a direct hit from another hijacked passenger jet.

Part of the five-sided structure collapsed and secondary explosions were reported as huge clouds of smoke rose from the wreckage.

Pentagon spokesman Glenn Flood said there were "extensive casualties and an unknown number of fatalities"

United Airlines has confirmed that two of its planes have crashed with 110 people on board. One was the aircraft that crashed in Pennsylvania - the crash site of the other has not been disclosed.

Flight chaos

Nearly all flights within the US have been grounded, while transatlantic flights to the country have been suspended.

 

World leaders have reacted with shock and outrage to news of the devastating attacks.

Among those sending messages of condolence were President Putin of Russia, UK Prime Minister Tony Blair and French Prime Minister Lionel Jospin.

However, some Palestinians and other Arabs have been celebrating the attack on the United States - seen by them as Israel's main sponsor.

People screaming

An eyewitness in New York told the BBC: "I came out of the subway, just after the first plane hit to scenes of absolute chaos. People were running away screaming.

"The sight of a hole in the side of the building was completely shocking. The neighbourhood is covered in a thick pall of smoke now the second tower has collapsed."

Briton James Winter, 30, living in an apartment close to the centre, said he was woken a huge blast at about 0800 local time.

"I was in bed and there was a huge explosion. The whole building rattled and shook," he said.

"I ran to the window and there was smoke billowing from the south side of one of the towers. Everyone in my building was panicking and running around."