US marks six months after attacks

The Tribute of Light will be lit every night until 13 April

The United States has marked six months since the 11 September attacks, with memorial ceremonies for the victims held around the country.

At a ceremony in New York City on Monday evening, two powerful vertical beams of light were switched on at the World Trade Center site, to the strains of "America the Beautiful".

Foreign dignitaries joined Mr Bush in paying tribute to the victims

The Tribute of Light symbolises the two destroyed towers and is visible up to 32 kilometres (20 miles) away.

At a ceremony in Washington, President George W Bush said the war on terror was entering its second phase.

"Every terrorist must be made to live as an international fugitive with no place to settle or organise, no place to hide, no governments to hide behind, and not even a safe place to sleep," he told an audience at the White House.

Early in the day other ceremonies to mark the past six months were held in Boston, at the Pentagon and in Pennsylvania.

In Shanksville, Pennsylvania, a candle was lit for each of those who died when United Airlines Flight 93 crashed into a field.

Tribute of light

Present at the White House commemoration were victims' relatives, members of Congress and the ambassadors of America's main allies.

Valerie Webb, 13, who lost her father in the attacks, switched on the beams

US Defence Secretary Donald Rumsfeld took part in the ceremony at the Pentagon.

In New York, 13-year-old Valerie Webb activated the 88 powerful searchlights arranged to simulate the twin towers, as relatives of some of the thousands killed looked on.

Valerie's father, Port Authority police officer Nathaniel Webb, died on 11 September, but his body has yet to be found .

"The lights will reach up to the skies and into heaven, near where the heroes are now," Arthur Leahy, whose brother, police officer James Leahy died in the attack, told the Associated Press.

The ethereal Tribute of Light memorial will shine each night until 13 April.

	A changed world World Trade Center death toll about 2,800; Pentagon 125 At least 3,600 civilian deaths in Afghanistan US military spending increased by 14% US forces deployed to Central Asian countries - including former Soviet republics  War on Terror: Six months on

Earlier, firefighters, survivors and relatives of victims of the attacks gathered near the remains of the World Trade Center to see the unveiling of a memorial to those who died.

The commemoration began with a moment of silence at 0846 local time (1346 GMT) - the exact time hijacked American Airlines Flight 11 was crashed into the north tower of the WTC.

A second silence was held 17 minutes later, in memory of the moment United Airlines Flight 175 ploughed into the south tower.

About 3,000 people lost their lives in the plane crashes and the collapse of the twin towers.

Many more died in the attack on the Pentagon and in another hijacked airliner that crashed in rural Pennsylvania.

The surviving sculpture is part of the memorial

A 45,000lb (20,400 kg) sculpture called The Sphere survived the destruction at the World Trade Center and has now become part of a temporary memorial in Battery Park, lower Manhattan, near the remains of the building.

The New York ceremony closed with the ringing of the bell from the New York Fire Department, which lost 343 members in the twin towers.