Commissioner Kelly says increased security measures are a precaution.
The New York Police Department is beefing up security at the city's synagogues and other Jewish sites this week for the Passover holiday in the wake of a deadly attack on a religious school in France last month.
Authorities stressed that there have been no specific threats reported in the city for the weeklong holiday, which starts at sundown Friday.
Police Commissioner Raymond Kelly said there would be heightened security and the deployment of heavily armed roving counterterrorism units.
"We'll ensure that coverage is more than adequate in those neighborhoods, adding foot posts, visits by officers to synagogues, outreach by community affairs officers, and a heightened presence of anti-crime," Kelly said Tuesday to a roomful of the city's Jewish leaders.
Kelly said the security measures were not related to the investigation of an online mock movie poster that warns that al-Qaida wants to return to New York City. The poster surfaced early Monday, and came from a forum where known terrorists have participated.
The department has kept a constant eye on militant groups for signs they might attack in New York, which has the largest Jewish population outside of Israel. The city faces constant threats in al-Qaida, the Hezbollah guerrilla group and so-called homegrown terrorists, Kelly said.
The NYPD dispatched extra patrols to more than 50 locations throughout New York last month on the news that an armed man on a motorbike had attacked a Jewish school in Toulouse, a southwestern city north of the Pyrenees mountains. The shooting left a rabbi, his two young sons and a schoolgirl dead.
There were no specific threats against New York then, either, but the department decided to take the measures as a precaution.
The nation's largest police department also discussed with leaders that it took similar precautions in 2008 after Imad Mughniyeh, a senior Hezbollah commander, was killed in a car bombing in Syria. The group blamed Israel for Mughniyeh's death.
A decade after the Sept. 11 attacks, "we know that counterterrorism is now a permanent part of our mission," Kelly said at the briefing.