NEW YORK -- Mourners in New York City observed moments of silence on the eighth anniversary of

  the Sept. 11, 2001, attacks.

Bells tolled at churches throughout the city Friday and hundreds gathered at a park by ground zero. They fell silent around 8:46 and 9:03 a.m., the times hijacked planes hit the Trade Center's two main towers. Two more moments of silence are planned in New York for the moments that each tower collapsed.

Vice President Joe Biden laid flowers at a reflecting pool in front of a smaller-than-usual crowd of just several hundred people. At a park southeast of ground zero, family members joined with volunteers who made firefighters meals or removed tons of debris from the smoldering trade center site to read victims' names. 

"By serving our communities and our country today and throughout the year, we commemorate our past while also preparing for our future," Ms. Napolitano said.

The attacks killed 40 people in Pennsylvania, 184 at the Pentagon and 2,752 in New York.

This year, one new name will be read -- a victim added to New York's death toll in January. The medical examiner's office ruled that Leon Heyward, who died last year of lymphoma and lung disease, was a homicide victim because he was caught in the toxic dust cloud just after the towers collapsed. It's the second time the city has added to the victims' list someone who died long after Sept. 11, ruling that exposure to toxic dust caused lung disease.

American troops in Afghanistan donned shorts and sneakers Friday to run in memory of the attacks, as they fight a war that was born of that day but now faces waning public support.

About 1,000 service members ran 5.5 miles at the main U.S. base, both to commemorate the anniversary and remember troops who have died in nearly eight years of fighting.

The U.S. and its allies first invaded Afghanistan in October 2001 to oust the Taliban regime for sheltering al Qaeda leaders who planned the attacks.

Organizers of Friday's race, which also was held at two other bases, called it an act of defiance against insurgents who have killed more American troops this year than in any other since the beginning of the conflict. August was the deadliest month for U.S. troops so far, with 51 killed.

"Our soldiers are running in the heart of Taliban territory, where the attacks on America were planned," a military statement said.