Security was a top priority Sunday at the start of the New York City Marathon amid cool temperatures and a stiff wind from the north, officials said.
This year's race marked the return of the marathon after a one-year hiatus due to superstorm Sandy.
The 47,000 runners are also competing for the first time since the April Boston Marathon bombing, which left three people dead and more than 260 injured.
Runners had to file through a security checkpoint before the start. Blue police department barricades blocked intersecting streets and police cruisers and ambulances were evident along the route.
The heavy security included a bomb-sniffing dog near the finish line and barricades around Central Park limit entry points, bag checks and scuba divers in the waters. There are also some 1,500 cameras along the running route, police officials said.
Shortly before 9 a.m. the first wave of wheelchair or handicapped racers zipped by Fourth Avenue and Union Street on wheels.
At 9:10 a.m. the professional women began their run, with the professional men starting at 9:40 a.m. Wave 2 of marathon runners went off at 10:05 a.m. with Wave 3 at 10:30 a.m and Wave 4 leaving at 10:55 a.m.
The race starts at the Verrazano-Narrows Bridge in Staten Island and goes through Brooklyn, Queens, Manhattan, The Bronx and back in Manhattan.
One spectator, Tom Wipf, 57, of Park Slope, said he noticed the increased police presence at this year's race.
Wipf, guitar player in band Hell or High water playing at the corner of Fourth Avenue and Union Street in Brooklyn, said this was the first year that bands received credentials that had their full names on them, along with bar codes for added security.
"We feel very safe here. It seems like the security presence are stepped up," he said.
The anti-terrorism operation at Sunday's New York City Marathon will be among the largest ever carried out across the five boroughs, as authorities employ new tactics in response to the Boston Marathon bombings, officials said.
Federal authorities and police are treating the marathon as a potential terrorist target, bolstering security to an unprecedented level for the event and working closely with U.S. intelligence agencies to sniff out any plots, according to a federal law enforcement source in New York with knowledge of the security measures and a city police official.
New elements of the plan include more bomb-sniffing dogs on patrol, high-tech explosives detection equipment, police boats and divers stationed on the city's waterways, intensive video surveillance, and the presence of thousands of additional private security workers, police officers and plainclothes law enforcement.
Spectators who want to cheer from the marathon finish line were screened for weapons and explosives. Any bag carried within blocks of the racecourse was searched. Participants in the marathon's opening parade were not allowed to march with bags, race officials said.