The NYPD is pulling out all the stops for the July Fourth weekend, deploying what is likely its largest counterterrorism operation ever for the national holiday, following overseas attacks and other activities motivated by the Islamic State group, officials said Wednesday.

Stressing familiar words -- that there is no known credible threat against New York City -- Commissioner William Bratton and his staff told reporters at a special crime briefing that the public should enjoy the holiday, including the East River fireworks show on Saturday, but remain watchful for anything suspicious.

"This may be potentially the most complex counterterrorism overlay for this event ever," said John Miller, the NYPD's deputy commissioner in charge of counterterrorism and intelligence.

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"That is not driven by any information or particular threat, as much as it is driven by the unfolding world events," said Miller, referring to three terror attacks last week overseas and recent arrests of what were called Islamic State-inspired terrorism suspects in the metropolitan area.

"The message is: Come to the fireworks, bring your families, have a great time because you are going to have one of the most well-police-protected events in one of the safest venues in the world," Miller said.

Chief of Department James O'Neill said there would be thousands of police officers out on patrol for the fireworks display, which will be launched from five barges, including a double barge just south of the Brooklyn Bridge.

For added security, police will use more critical response vehicles and a citywide "strategic response group," heavily armed Hercules teams, canine cops and radiation-detecting devices on the ground, in the waterways and in the air with police helicopters. Individual police officers also will wear miniature radiation detectors, O'Neill said.

Miller said there also will be measures taken that aren't necessarily visible to the public.

"We will be leveraging the 7,000 cameras that are part of our domain awareness system, particularly focused in the lower Manhattan security initiative," Miller said.

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On Long Island, Nassau police continue to "remain on heightened alert based upon the latest intelligence regarding terrorist threats directed towards law enforcement," Insp. Kenneth Lack, a spokesman for the department, said in an email. And Suffolk police said they plan Thursday to announce increased enforcement as well address summer safety, including boating, beaches and pools.

For intelligence gathering, the NYPD will have special teams monitoring calls to the "If you see something, say something" line -- 877-NYC-SAFE -- to immediately check leads, Miller said.

Intelligence officers in special cars also will be located on both sides of the East River to respond to any calls or suspicious incidents, while other NYPD analysts will scan social media for leads, police said.

"Some groups, particularly ISIS, have been very active in social media," giving tips and clues about potential actions, Miller said.

NYPD teams also will visit hotels to invite employees and guests to phone in any tips about suspicious activities.

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Bratton said about 400 new officers of about 1,300 being added to the NYPD this year will go to counterterrorism because of the emergence of the terror group, also known as ISIS or ISIL.

"Is there an enhanced initiative this year? There is," Bratton said. "Next year, you will probably see more."