America has been devastated by a wave of terrorist attacks on major political and industrial targets, prompting mass evacuations in the US and precautionary evacuations in London.

Two planes - reportedly a Boeing 737 and a 767- crashed into New York's World Trade Centre at around 9:30am local time (1:30pm British time), causing the famous 'twin towers' to collapse completely into the streets below.

Shortly after, another plane crashed into the Pentagon in Washington and a fourth plane crashed south-east of Pittsburgh.

Terrorist group the Democratic Front for the Liberation of Palestine are reported to have claimed responsibility for the attacks.

President George W Bush has vowed to "hunt down" those responsible for what has become the most significant peace-time terrorist attack in history.

Potential targets in London, including England's tallest building, Canary Wharf, were evacuated as a precautionary measure and all flights into the US have been diverted or cancelled.

US fighter planes patrolled the skies above New York and Washington as President Bush ordered any plane left flying in the skies above the cities be shot down.

Exact numbers of casualties are currently unknown, but at peak times the World Trade Centre can contain up to 100,000 workers. The three planes were also thought to contain significant numbers of passengers.

World leaders have joined in the global condemnation of the attacks and Prime Minister Tony Blair has backed President Bush's vows to bring the terrorists to justice.