TWO hijacked planes crashed into the World Trade Centre in New York today in an apparent terrorist attack

And the FBI has launched a major investigation after it was believed the planes had been hijacked shortly before the disaster.

One of the planes, en route to Los Angeles was hijacked in Boston. There was also a massive explosion at the Pentagon in Washington - and The White House was being evacuated.

The Democratic Front for the Liberation of Palestine has reportedly claimed responsibility.

Thousands of people were injured and at least six killed as huge fireballs ripped through the building.

The crash at the popular tourist destination, the fourth largest building in the world, happened just before 2pm British time today.

Reports said that it appeared that two United American 767 planes had smashed into the office block, which includes bars and restaurants. Both of the planes were described as twin-engined jet aircrafts.

One was believed to have been a passenger plane.

One was left embedded in the top quarter of the building, which is on one of the world's busiest air routes, with smoke billowing across the New York sky line.

Tonnes of debris began pouring off the building as explosions were heard across the city, which was thrown into mass confusion.

Flashes of fire were also spotted coming from the twin towers.

The crash occurred at 9am US time just as trading at the financial centre, which includes a massive under ground shopping centre, was about to start.

An eyewitness said the plane appeared to hit one of the skyscraper's twin towers about 20 floors from the top.

Another, Jeanne Yurman, said she was watching TV when she heard what she thought was a sonic boom. ''I thought it was Concorde,'' she said.

Smoke was pouring out of two sides of the top floors of the building.

US President George W Bush was due to make a statement on the tragedy later today.

The World Trade Centre complex has a total of 12 million cubic feet of rented space in its seven buildings including four million cubic feet in each of the twin towers that were hit.

Around 50, 000 people work in some 500 companies and organisations located in the complex.

A further 70,000 tourists and business people visit the impressive towers every day

Another eye witness Joseph Cappucci added: '' I saw the plane come over head it started to bank and disappeared over the telephone building.

''It looked like a 747. I could see it going down. I could see he was in trouble by the way he was turning.''

Another eye witness added: ''This is absolutely catastrophic. The smoke is ripping across the sky line.''

The towers were struck by bombers in February 1993.

''The plane was coming in low and it looked like it hit at a slight angle,'' said Sean Murtagh, a CNN vice president.

Large holes were visible in sides of the 110 storey buildings, landmark twin towers.

The tops of the twin towers on the southern tip of Manhattan, were obscured by the smoke.

Thousands of pieces of what appeared to be office paper came drifting over Brooklyn, about three miles from the tower, one witness said.

The centre bombing in February 1993, killing six people and injured more than 1,000 others.

In 1945, an Army Air Corps B-25, a twin-engine bomber, crashed into the 79th floor of the Empire State Building in dense fog.