AKIPRESS.COM - Led by President Barack Obama, Americans commemorated the 13th anniversary of the Sept. 11, 2001, attacks on Thursday by observing moments of silence for the thousands killed that day at New York City's World Trade Center, the Pentagon and a Pennsylvania field.

In what has become an annual ritual, relatives began slowly reciting the nearly 3,000 names of the victims at a ceremony in lower Manhattan, from Gordon Aamoth Jr. to Igor Zukelman.

Readers would occasionally pause as a silver bell was rung to mark the exact times when each of the four planes hijacked by al Qaeda militants crashed at the three sites and when each of the World Trade Center's twin towers collapsed. With each bell, a moment of silence was observed.

Obama spoke at the Pentagon during a private ceremony for relatives of the 184 people killed in the attack on the U.S. Department of Defense headquarters in Arlington, Virginia, several miles from the White House.

He laid a wreath of white lilies and chrysanthemums, and kept his hand on his heart as "Taps" played.

Many people held up posters with smiling photographs of their dead relatives. Red roses and American flags poked up from the bronze plates bearing victims' names that ring the two waterfalls that now trace the footprints of the fallen towers.

New York Governor Andrew Cuomo, New York City Mayor Bill de Blasio and two former mayors, Michael Bloomberg and Rudy Giuliani, were among the mourners.