Barack Obama, Michelle Obama, George W Bush and Laura Bush
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US remembers 9/11 ten years on

11 September 2011 Last updated at 16:58 BST

Ceremonies are being held in the US to honour the victims of the 9/11 attacks, 10 years after the event.

Nearly 3,000 people died when four hijacked airliners were crashed into the World Trade Center in New York, the Pentagon and a Pennsylvania field.

Mark Mardell reports.