Moments of silence for the dead, and pleas to come together

The United States marked the 20th anniversary of the Sept 11 attacks on Saturday with pleas for unity at solemn ceremonies.

At the 9/11 memorial in New York, the official ceremony was attended by US President Joe Biden and former presidents Barack Obama and Bill Clinton.

The service at Ground Zero where 2,753 people died－some of whom jumped to their deaths from the burning towers of the World Trade Center－took place under tight security, with Lower Manhattan effectively locked down.

The first of six moments of silence was marked at 8:46 am, with a bell ringing to symbolize the time the first hijacked plane crashed into the north tower.

Heart-wrenching commemorations also took place at the Pentagon and Shanksville, where George W. Bush, then president on 9/11, said the unity the US showed following the attacks "seems distant" from today.

Bush warned against domestic extremism, saying the country has seen "growing evidence that the dangers to our country can come not only across borders but from violence that gathers within".

Agencies - Xinhua