Rifle-toting snipers, police officers and even a military helicopter swarmed around Ground Zero Wednesday.
New York officials imposed citywide security measures to prevent any disruption of the anniversary ceremony at the World Trade Center site.
Circling above Wednesday morning's ceremony was a camouflaged military helicopter with protruding gun turret.
Just south of the site, police set up two decontamination tents as a precaution. Undercover police officers also were deployed throughout the crowd.
Around the city's police headquarters, some guards were seen carrying rifles for the first time in months.
Patrols around city landmarks, bridges and tunnels have been strengthened, as well.