AP Photo/Chris HondrosA mourner holds a picture of a victim of the Sept. 11 terrorist attacks before the start of a memorial ceremony Thursday, Sept. 11, 2008 in New York. Throngs of family members of victims and others gathered in lower Manhattan for the annual ceremony.
NEW YORK " Relatives of victims killed at the World Trade Center are observing moments of silence to mark the seventh anniversary of the Sept. 11 terrorist attacks.
The ceremony at ground zero included moments of silence at 8:46 a.m. and 9:03 a.m. " the times that two hijacked jets slammed into the twin towers. Two more moments of silence were to be held at the times the towers fell.
Mayor Michael Bloomberg opened the ceremony by telling the tearful audience: "Today marks the seventh anniversay of the day our world was broken."
Other ceremonies are being held throughout the day around the country, including in Washington and in Pennsylvania. Barack Obama and John McCain are due at ground zero to pay silent respects.