Families remembered their loved ones 20 years after the 9/11 terror attacks in the US, with grieving relatives vowing to “never forget” those who lost their lives.

Six moments of silence were observed in New York City to mark the moments when four commercial planes crashed and when the the two World Trade Center towers crumbled, killing nearly 3,000 people.

The planes had been hijacked by terrorists on the morning of 11 September 2001.

Two were flown into the World Trade Center towers in New York City just before 9am local time, a third crashed into the west side of the Pentagon at 9.37am, while the fourth flight crashed in rural Shanksville, Pennsylvania, at 9.57am after passengers tried to overpower the hijackers and take control of the plane.

US President Joe Biden and former presidents Barack Obama and Bill Clinton were among hundreds of people who gathered at the site where the two trade centre towers fell two decades ago.

Each of them wore blue ribbons and held their hand over their heart as a procession marched a flag through the memorial. Some of those gathered at the memorial carried photos of loved ones killed in the attacks.

The names of all 2,977 victims were read out and Mr Biden, who was as senator at the time of the attacks, wiped a tear from his eye at one point, but he did not speak at the event.

Those who did speak shared heart-breaking tributes to those they lost.

One described the “unbearable sorrow and disbelief”, another remembered a “beloved sister… she had a habit of saying ‘get over it’ and, Cathy, I can tell you we have never gotten over it”.

One man paid tribute to his brother “who we continue to love and miss every day – the world is a lesser place without him”.

Another said: “I couldn’t believe that you’re gone – I just want to say I love you and I miss you”, while one speaker remembered their father, saying: “Dad, we miss you every day”.

Bruce Springsteen sang his song I’ll See You In My Dreams, accompanying himself with the guitar and harmonica, his words echoing the hopes expressed by families still grieving.

“I’ll see you in my dreams.

“We’ll meet and live and love again.

“I’ll see you in my dreams.

“Yeah, up around the river bend.

“For death is not the end.

“And I’ll see you in my dreams.”

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Vice president Kamala Harris and George W Bush – who was president at the time of the attacks – were among those who gathered at the Flight 93 National Memorial in Pennsylvania.

Ms Harris praised the courage and resilience of Americans who united in the days following the attacks, saying: “In a time of outright terror, we turned toward each other.

“If we do the hard work of working together as Americans, if we remain united in purpose, we will be prepared for whatever comes next.”

Mr Bush said: “So much of our politics have become a naked appeal to anger, fear and resentment.

“On America’s day of trial and grief, I saw millions of people instinctively grab for a neighbour’s hand, and rally for the cause of one another. That is the America I know.”

Mr Biden also visited Shanksville later on Saturday, before heading to the Pentagon.

In a video released on Friday night, Mr Biden had said: “Children have grown up without parents, and parents have suffered without children.”

But he also said shared what he called the “central lesson” from the attacks: “That at our most vulnerable… unity is our greatest strength.”

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Earlier, former president Mr Obama reflected on the lessons that had been learned in the “20 years since that awful morning”.

In a statement, he said: “That list of lessons is long and growing. But one thing that became clear on 9/11 – and has been clear ever since – is that America has always been home to heroes who run towards danger in order to do what is right.

“For Michelle and me, the enduring image of that day is not simply falling towers or smouldering wreckage. It’s the firefighters running up the stairs as others were running down.

“The passengers deciding to storm a cockpit, knowing it could be their final act.

“The volunteers showing up at recruiters’ offices across the country in the days that followed, willing to put their lives on the line.

“Over the last 20 years, we’ve seen the same courage and selflessness on display again and again.”

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He said the US had seen the same courage today, with doctors and nurses battle through the COVID crisis and military personnel risk their lives in Afghanistan.

Mr Obama added: “9/11 reminded us how so many Americans give of themselves in extraordinary ways – not just in moments of great crisis, but every single day. Let’s never forget that, and let’s never take them for granted.”

Former president Donald Trump was not at the anniversary ceremonies but released a video in which he spoke of the sadness of 9/11 and attacked Mr Biden over the withdrawal from Afghanistan.

Mr Trump is expected to provide commentary for a boxing match headlined by 58-year-old former heavyweight champion Evander Holyfield later on Saturday.

British Prime Minister Boris Johnson was among the world leaders to offer support to the US as people remembered the 9/11 attacks.

He said the terrorists had “failed to drive our nations apart, or cause us to abandon our values, or to live in permanent fear”.

French President Emmanuel Macron added: “We will never forget. We will always fight for freedom”, while South Korea’s President Moon Jae-in sent his “deepest condolences”, describing the losses of 9/11 as a “deep wound”.