WASHINGTON (AA) – The US on Sunday marked the 21st anniversary of the Sept. 11, 2001 terror attacks, during which roughly 3,000 people were killed when al-Qaeda hijackers struck the financial and political capitals of the US.

“21 years ago, 21 years, and we still kept our promise. Never forget. We’ll keep the memory of all those precious lives stolen from us,” President Joe Biden said during an event at the Pentagon.

Besides the event at the Pentagon, where 184 people were killed after a hijacked American Airlines plane crashed, ceremonies were held at Ground Zero, New York, where World Trade Center’s twin towers were destroyed, and Shanksville in the US state of Pennsylvania.

Vice President Kamala Harris and husband Doug Emhoff joined the observance at Ground Zero, while first lady Jill Biden was in Shanksville to mark the anniversary of the 9/11 terror attacks.

During all three observances, the names of the victims were read.

“America itself changed that day,” said Biden. “But what will not change, and never will, is the character of this nation that the terrorist thought they could wound.”

Slain al-Qaeda leader Osama bin Laden claimed responsibility for the coordinated attacks.

The president said it took 10 years to hunt down and kill bin Laden, and recalled his order to authorize the strike to kill Ayman al-Zawahri, a top al-Qaeda figure close to bin Laden, one month ago.

“We will not rest. We’ll never forget. We will never give up. Our commitment to preventing another attack on the United States is without end,” said the US president.

“We raised monuments and memorials to the citizens whose blood sacrificed on this (Pentagon) ground and then Shanksville, and Ground Zero, to keep touch of the memory, keep it bright for all the decades to come,” he added.

In his remarks, the US president also touched on the unity of the nation, saying: “We also had to face down the worst impulses, fear, violence, discrimination directed against Muslim Americans, as well as Americans of Middle Eastern and South Asian heritage.”

“There’s nothing this nation cannot accomplish when we stand together and defend with all our hearts. That was what makes us unique in the world,” he added.

The perception of Muslim people after the terror attack changed dramatically, especially after the US adopted the “War on Terror” policy under then-President George W. Bush.

According to FBI statistics, hate crimes against Muslims skyrocketed immediately after 9/11, rising 1,617% from 2000 to 2001, marking some of the highest numbers of Islamophobic hate crimes ever seen in America.