In pictures: Silence and tears as US remembers 9/11 attacks - BBC News
Ceremonies are held in New York, Virginia and Pennsylvania to mark the lives lost 20 years ago.
The US has been remembering the 2,977 people who died when four passenger planes were hijacked by al-Qaeda militants and crashed into the World Trade Center and the Pentagon 20 years ago.

The first of six moment's of silence began with the ringing of a bell at the exact time the first plane hit the North Tower of the World Trade Center.

The bell rang again when the second plane crashed into the South Tower; when each of the towers fell; when a third jet struck the Pentagon; and when a fourth plane crashed into a field in Pennsylvania.

The names of each of the victims was read out during the ceremonies. Family members took turns to read out the names, paying tribute to the loved one they had lost.

Many of those who lost their lives in New York were firefighters who had gone into the two towers to try and get people out.

In total, 441 first responders were killed, the largest loss of emergency personnel in US history.

At the memorial in New York, President Joe Biden and First Lady Jill Biden were joined by former Presidents Bill Clinton and Barack Obama, as well as former First Ladies Hillary Clinton and Michelle Obama.

George W Bush, who was president when the attacks happened, attended the ceremony in Shanksville, Pennsylvania, where the fourth plane came down after its passengers and crew overpowered the hijackers.

The 184 people who lost their lives in the attack on the Pentagon were remembered at a ceremony outside the Department of Defense headquarters just outside Washington DC.

Bruce Springsteen played I'll See You in My Dreams during the ceremony in New York to a silent crowd, with some gently swaying to the music.

The twin beams of the Tribute in Light illuminated the New York skyline as a memorial to all those who lost their lives in the terror attacks.