Watch live: Pentagon ceremony marks 23 years since September 11 attacks

Watch live as a 9/11 observance ceremony is held at the Pentagon on Wednesday to mark the 23rd anniversary of the September 11, 2001, attacks on the United States.

On this day in 2001, al-Qaeda terrorists hijacked commercial planes and crashed them into the World Trade Center and the Pentagon, killing 2,977 people.

The Pentagon ceremony comes as the Bell of Hope is rung in New York City to remember the victims.

Joe Biden and Kamala Harris will mark 23 years since the attacks at a commemorative ceremony in the city, visiting each of the three sites where hijacked planes crashed.

They will first visit the site where planes brought down the World Trade Center's twin towers.

Biden and Harris will then fly to Shanksville, Pennsylvania, where passengers on United Flight 93 overcame hijackers and the plane crashed in a field, preventing another target from being hit.

They will then go back to the Washington area to visit the Pentagon memorial.

According to his campaign, Donald Trump will also attend ceremonies in New York and visit Shanksville.