9/11 attacks: US President Biden to mark 21st anniversary, tributes pour in

As America remembers 9/11 with moments of silence, US President Joe Biden will mark the 21st anniversary of the attacks at the Pentagon on Sunday. President Joe Biden plans to speak and lay a wreath at the Pentagon, while first lady Jill Biden is scheduled to speak in Shanksville, Pennsylvania. Vice President Kamala Harris and her husband are due at the World Trade Centre in New York, new agency AP reported.

The New York City Police Department dedicated its Twitter account today to remembering "our 9/11 fallen brothers and sisters". The NYPD shared portraits of officers that it lost during the attack.

Indian Union Minister Hardeep Singh Puri paid his tribute to those who suffered from the attack on the United States' Twin Towers and tweeted: "On the anniversary of 9/11, I pay tribute to the victims of the dastardly terror attacks which changed the world forever."

On September 11, 2001, nearly 3,000 people were killed as 19 al-Qaeda hijackers seized control of four jetliners, sending two of the planes into New York's World Trade Centre, one into the Pentagon and the fourth into a field in western Pennsylvania. The terror attack defined the presidency of George W. Bush, who was reading a book to Florida schoolchildren when the planes slammed into the World Trade Centre.