U.S. President Joe Biden and leaders of several countries made statements honoring those who died 20 years ago in the September 11, 2001, terrorist attack, the largest in U.S. history. On that day, 19 al-Qaida terrorists hijacked four commercial planes and attacked several targets in New York City, Washington, D.C., and near Shanksville, Pennsylvania.

Mourning ceremonies take place in New York, Pennsylvania, and on the outskirts of Washington every year on 9/11. Family members of nearly three thousand victims gathered in downtown Manhattan, at Shanksville Field, at the Pentagon, at the 9/11 memorial on the spot where the World Trade Center twin towers stood and then collapsed when the hijacked planes flew into each of them.

The ceremony of reading out the names of the victims of the attack on the World Trade Center lasted more than four hours online. Six episodes of a moment of silence took place – in keeping with the time when the Twin Towers fell, when the plane fell on the Pentagon and when the fourth plane crashed.

European leaders' statements

In a video message released on the eve of the anniversary, Joe Biden recalled the 2,977 lives lost in the attack. "In the days following 9/11, we saw heroism everywhere, where it was expected and expected. And we saw something quite rare -- a real sense of national unity... In the battle for America's soul, unity is our greatest strength. That doesn't mean we have to believe in one thing -- it's about having fundamental respect and belief in each other and this nation," said the president of the United States.

Britain's Queen Elizabeth II said her prayers are with those who died and survived the attacks and noted the contributions of all those who helped restore normalcy after the tragedy. British Prime Minister Boris Johnson said the attacks did not undermine the Western world's faith in freedom and democracy.

"The horrific attacks of 9/11 twenty years ago changed the course of history.

We remember the victims and the noble sacrifices of the many people who rushed to help after the attack. The EU will continue to be an ally of the U.S. in the ongoing fight against terrorism and extremism in all its manifestations," said European Council President Charles Michel.

"Even in the darkest, most testing moments, the best human qualities can emerge.

The EU supports the U.S. in defending freedom and compassion instead of hatred," said European Commission President Ursula von der Leyen.

"Today, we mourn all those who died, and we sympathize with those who lost loved ones in the 9/11 attacks, who were seriously injured ... We must reflect critically on what happened after 9/11. Recent events in Afghanistan were a very harsh reminder of that," said German Foreign Minister Heico Maas, adding that the contributions of the people who helped build democracy in that country are still significant and valuable.

"I am convinced that we must continue to work for peace and security in the world in different ways. Staying on the sidelines is the worst way to serve our interests and guarantee our own security. Part of the answer is in restoring our allied cooperation, and especially on this day - reaffirming our friendship and partnership with the United States," Maas added.

"Today is the 20th anniversary of the horrific 9/11 attacks ... We must continue to fight Islamist terror and radicalization together with the United States," Austrian Chancellor Sebastian Kurz wrote.

Poland's president laid a wreath at the memorial plaque to those killed in the attack in the chapel of the presidential palace. "These events changed the world forever ... We remember 9/11," the presidential office said in a statement.

"We will never forget and will always fight for freedom," French President Emmanuel Macron said.