"Today we mark a somber day seared in the minds of millions of people around the world, a day when nearly 3,000 lives from over 90 countries were taken by terrorists in cowardly and heinous attacks in the United States of America. Thousands more were injured," Guterres said in the statement.

 

"On this day, my thoughts are with the victims and their families. We pay tribute to the survivors, who have had to overcome physical and emotional scars to get on with their lives. We honour the first responders who put themselves in harm's way, with many making the ultimate sacrifice, exemplifying the very humanity and compassion that terrorism seeks to erase.

 

"And we remember the solidarity, unity and resolve expressed 20 years ago by the international community, aiming for a future without terrorism.

 

"Today, we stand in solidarity with the people of New York City, the United States of America, as well as all victims of terrorism everywhere around the world.

 

"We recommit ourselves to work together to uphold their rights and needs," Guterres added.

 

The September 11, 2001, attacks were a series of four coordinated terrorist attacks carried out by the Al Qaeda terror group.

 

Four commercial planes were hijacked by 19 Al Qaeda terrorists.

 

The first plane to hit its target was American Airlines Flight 11. It was flown into the North Tower of the World Trade Center complex in Lower Manhattan.

 

Seventeen minutes later, the World Trade Center's South Tower was hit by United Airlines Flight 175.

 

Both 110-storey towers collapsed within an hour and 42 minutes, leading to the collapse of the other World Trade Center structures and damaging surrounding buildings.

 

The third plane, American Airlines Flight 77, crashed into the west side of the Pentagon causing a partial collapse of the building's side.

 

The fourth jet, United Airlines Flight 93 which was flown in the direction of Washington, D.C., was the only onenot to hit its intended target, instead crashing in a field near Shanksville, Pennsylvania.

 

It was later determined that Flight 93's target was either the White House or the Capitol.

 

A total of 2,996 people were killed in the attacks, which were the deadliest in human history, with more than 25,000 others injured.