Names of those killed in the attacks were read out by family members and volunteers. Similar ceremonies were held in past years.

'From this day forward we will safeguard the memories of those who died by remembering the spirit of service that led our city with hope and helped to keep us strong,' Bloomberg said.

Another ceremony was held at 10:03 a.m. in Shanksville, Pennsylvania, to remember the 40 victims of United Flight 93 that crashed there at that time. Former secretary of state Colin Powell attended the ceremony.

The New York Daily News also published a message by Obama, who said the 2001 attacks were a 'tragedy that will be forever seared in the consciousness of our nation'.

'No one can guarantee that there will never be another attack,' Obama said, but pledged his responsibility to protect the security of the American people. He said his administration is taking steps to fight terrorism, such as tightening border security and building new partnerships around the world to dismantle Al Qaeda.