New York City will enhance security at the world's largest marathon this weekend by deploying more police officers, bomb-sniffing dogs, helicopters and patrol boats than last year following a reported threat of militant attacks ahead of Tuesday's election.
The city was on heightened alert after federal authorities said on Friday they were aware of an unspecific threat of attacks by the al Qaeda militant group around Election Day.
For Sunday's (Monday AEDT) marathon, the number of uniformed and plain-clothes officers assigned to the race will be 10 per cent more than for last year's and other resources have also been increased, police said.
The increases were first announced on Wednesday.
"The people of New York should feel safe," Police Commissioner James O'Neill said on CNN. "We do large events in New York City like no other city."
Tensions in the biggest US city were raised in September when a pressure cooker bomb exploded on a footpath in Manhattan's Chelsea neighbourhood, wounding 31 people and evoking memories of the 2013 Boston Marathon bombing.
In New York this weekend, police will run screening checkpoints near the start and finish of the race, as well as mobile cameras and units to detect radiation, the department said. Some officers will be on horseback, as is common in the city.
For security reasons, runners are prohibited from running with a backpack, and the only bag they can check is one provided by race officials.
More than 50,000 people from around the world are expected to finish the 26.2-mile (42.2 km) marathon as millions of spectators cheer them on.
