The US has marked the 15th anniversary of 9/11 with a moment of silence marking the instant when a hijacked plane crashed into the World Trade Center.
At Ground Zero, hundreds of victims' relatives as well as dignitaries gathered to hear the reading the names of the nearly 3,000 people killed on the morning of September 11, 2001.
Bereaved father Tom Acquaviva, who lost his son, said: "It doesn't get easier. The grief never goes away. You don't move forward - it always stays with you.”
President Barack Obama was set to speak during a ceremony at the Pentagon as part of a day of commemorations.
Hundreds of people also were expected for a service at the Flight 93 National Memorial in Shanksville, Pennsylvania.
Nearly 3,000 people died when hijacked planes slammed into the World Trade Centre, the Pentagon and a field near Shanksville. It was the deadliest ever terror attack on American soil.
The 15th anniversary comes amid a fierce presidential campaign between Democrat Hillary Clinton and Republican nominee Donald Trump.
Both attended the anniversary ceremony at the World Trade Center but did not speak. TV ads have also been suspended for the day.
