Americans today marked the 13th anniversary of the September 11, 2001 attacks with President Barack Obama pledging that the US would never "give in to fear."
Somber ceremonies of remembrance were held in New York and Washington, against the backdrop of Obama's pledge to "destroy" Sunni militant group Islamic State which has seized the control of a large swathe of lands in Iraq and Syria.
"As Americans, we draw strength from you, for your love is the ultimate rebuke to the hatred of those who attacked us that bright, blue morning," Obama said to relatives of victims at the Pentagon -- scene of one of the 9/11 strikes.
"You've kept alive a love that no act of terror can ever extinguish. We carry on because as Americans, we do not give in to fear. Ever," he added.
Earlier, Obama, his wife Michelle and Vice President Joe Biden observed a moment of silence on the White House south lawn, along with about 300 staffers. Flags in Washington flew at half-mast.
In New York, relatives of the people who died when hijacked airliners slammed into the World Trade Center gathered at Ground Zero to remember the dead. The ceremony began with a moment of silence at 8:46 am (1246 GMT), when the first plane smashed into the Twin Towers.
The family members then began the long process of reading the names of the nearly 3,000 people who were killed in the attacks on New York, the Pentagon and in Shanksville, Pennsylvania.
This year the 9/11 museum in New York will be open on the anniversary of the attacks.