NEW YORK (CBSNewYork) —  The NYPD is on high alert following a new threat by Islamic State extremists.

Officials said ISIS posted a video on Twitter on Saturday calling for attacks on police officers and soldiers in the United States, Canada, Great Britain and France.

Speaking Monday on “CBS This Morning,” Police Commissioner Bill Bratton said the NYPD takes the threats seriously.

“There are a number of people who are in the process of being radicalized,” he said. “Something like this can be the last straw to move them forward. Additionally, they are continually working to attract new recruits.”

John Miller, the NYPD’s deputy commissioner of intelligence and counter-terrorism, said Sunday the message put out by ISIS was a renewal of a call from mid-September, just before a series of attacks in Canada and a hatchet attack against NYPD officers in October. The FBI said the man responsible for the New York attack was inspired by terrorist videos.

As WCBS 880’s Marla Diamond reported, Miller said the NYPD is also on alert for copycats after the attack on the Charlie Hebdo satirical newspaper, and the subsequent standoffs, in Paris.

Long Island U.S. Rep. Peter King, (R-N.Y.), said he’s worried more police officers will be attacked.

“ISIS is more dangerous than al Qaeda in this respect: They have experts handling their media,” King told CBS2’s Matt Kozar. “They can appeal to people on the edges of society.”

Miller said the NYPD issued an advisory to police officers informing them of the message and reminding them to be “extra vigilant.”

“Pay attention to your surroundings and pay close attention to approaching vehicles,” the memo reads in part. “Pay close attention to people as they approach and look at their hands.”

Miller said the NYPD has not detected a threat specific to New York, but security has been stepped up in many locations, including Times Square, and at some facilities in the Jewish community, CBS2’s Tony Aiello reported.

“They’re there for a purpose — to protect that location as well as themselves and the public,” Bratton said of officers at fixed posts.

The agency’s counterterrorism officers and civilian analysts are also studying the Paris attacks on Charlie Hebdo satirical newspaper and a kosher grocery store to learn how they might better protect New York, Miller said.

“Our foreign posts, including our detective assigned to the French national police have been forwarding that information on a minute-by-minute basis, and we’ve been evaluating it and analyzing it,” Miller said.

Mayor Bill de Blasio also said the NYPD and the city are always on the lookout for threats and terrorist activity.

“We are the number one terror target, and that has created in us a sense of vigilance every day. There is no down day. There is no day when we’re less vigilant. We’re vigilant every day,” de Blasio said. “We have 1,000 counterterrorism officers who do extraordinary work, but when a tragedy like this occurs, we reinforce additionally any location we believe to be sensitive.”

The department’s counterterrorism officers stationed around the world are equipped with the latest technology that surpasses that of many countries, de Blasio said.

U.S. Sen. Robert Menendez (D-N.J.) said he hopes the U.S. intelligence community is prepared to prevent a strike similar to last week’s attacks in Paris.

“What we have to do is be able to create a sense in communities of the importance of high alert, of vigilance, of being able to share information,” the New Jersey Democrat told WCBS 880’s Peter Haskell.

Menendez said one key is enforcing no-fly lists.

De Blasio said the public should be reassured that perceived tension between the feds and the NYPD under previous Commissioner Ray Kelly has been healed.

“The working relationship between the NYPD and the federal agencies that protect us is at an all-time high,” de Blasio said. “It’s at its most productive, most communicative, and that will also benefit the people of this city in terms of keeping us safe.”

Meanwhile Monday night, extra security was posted at the Eiffel Tower and in the Jewish District of Paris in the wake of the terror attacks there. Officials fear as many as six additional members of the terror cell responsible for the attacks last week may be preparing to strike again.

Security has also been stepped up at train stations and Jewish facilities in New York in response to the Paris attacks.

And federal officials were probing a hack into the U.S. Central Command’s Twitter and YouTube sites by a group that purported to represent a part of ISIS.

The hack apparently started at 12:30 p.m. with a message sent via the Twitter account for the U.S. Central Command, or Centcom, that read, “American soldiers, we are coming, watch your back. ISIS.”

A message went on to say that “ISIS continues its CyberJihad,” adding “we broke into your networks and personal devices and know everything about you.”

“ISIS is already here, we are in your PCs, in each military base,” the message read. “We know everything about you, your wives and children.”

Further Tweets on the page included names, phone numbers and email addresses of various military commanders. An outdated list of retired generals and their contact information was also posted.

Various military scenarios involving North Korea and China were also posted.

The military suspended the Twitter site and terminated the YouTube site. This is not the first time that U.S. government websites or other accounts have been hacked. It was not clear whether the site was attacked by the insurgent group or by sympathizers.

On Thursday night, nine NYPD officers were on their way to Paris to attend the funerals for the French police officers killed in the terror attacks last week, CBS2’s Aiello reported.

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