(VOVworld) - Ceremonies have been held commemorating 3,000 victims of the terrorist attack on September 11th, 2001. More than 1,000 people gathered at the National September 11 Memorial plaza in New York, built on the collapsed the World Trade Center, for the annual reading of the names of victims killed in the attack. In Washington, President Barack Obama and Vice President Joe Biden attended memorial services in the White House and then the Pentagon. Obama called on all Americans to unite to defend the US. The commemorations were held in other US cities and its military bases in other countries.

U.S. President Barack Obama, first lady Michelle Obama, Vice President Joe Biden and Jill Biden (L-R) pause for a moment of silence on the 12th anniversary of the attacks of September 11, 2001. (Photo: Reuters)

On September 11^th, 2001, 19 Al-Qaeda hijackers took control of 4 civil planes. 2 of them flew to the 110-storey towers of the World Trade Center. The other 2 crashed into the Pentagon and the Pennsylvania field.