Members of the NYPD's counterterrorism unit patrol in Times Square in New York on October 12.
CNN  — 

With a war ongoing between Israel and Hamas, law enforcement agencies across the US remain on high alert, with a joint bulletin Wednesday warning of the threat of “lone offenders” as sources say officials are using an array of sophisticated tools and techniques to monitor for potential threats.

The FBI and the Department of Homeland Security, along with the National Counterterrorism Center, issued the Joint Intelligence Bulletin sharing information and a threat assessment advising state and local law enforcement agencies that “lone offenders inspired by, or reacting to, the ongoing Israel-HAMAS conflict pose the most likely threat to Americans.”

The bulletin – obtained by CNN – also notes “the FBI has seen an increase in reports of threats against faith communities, particularly Jewish and Muslim communities.” While Hamas has not specifically called for attacks on US soil, the bulletin says, other foreign terrorist organizations have called for attacks in the US, which “may prompt homegrown extremists” to direct attacks at Israeli, Jewish or US government targets.

In reaction to the conflict, police in New York City are operating in a heightened threat posture: A Tuesday night teletype message to 33,000 police officers ordered thousands of detectives and high-ranking officials who normally work in plain clothes to show up in uniform until further notice.

The order read in part, “Effective immediately and until further notice, all members of the service, in every rank, will perform duty in the uniform of the day and be prepared for deployment.” The order also directed officers in police cars to patrol with their flashing lights to increase visibility.

While New York Mayor Eric Adams and police officials have repeatedly said that there is no known “specific, credible threat” to the city, these steps indicate an understanding that the events in Gaza – particularly the blast at a hospital in which the Hamas-controlled Palestinian Health Ministry says hundreds were killed – have ratcheted up what was already a heightened threat environment.

FBI working ‘around the clock,’ source says

Federal and local law enforcement officials around the US are using sophisticated tools and techniques as they continue to monitor for potential threats, several law enforcement sources told CNN.

FBI counterterrorism agents and analysts in bureau divisions continue to work “around the clock” to field tips from the public and monitor overseas online forums frequented by extremists, according to one federal law enforcement source who works national security cases.

Federal agents are also tasking human sources reporting on terrorism matters to help identify potential plots, another source said, and using informants to identify previously unknown email accounts, phone numbers and messaging apps used by known or suspected terrorists.

In a call with reporters on Saturday, FBI officials said the agency had seen an increase in reported threats against Jewish and Muslim Americans following the Hamas terrorist attack and were working to determine whether any were credible.

“We’ve been leveraging every tool at our disposal to protect the American people from extremist violence,” said one senior FBI official, including by “monitoring sensitive collection.”

Detection tools frequently used by FBI counterterrorism personnel include court-authorized monitoring under the Foreign Intelligence Surveillance Act, and so-called 702 collection authority for national security targets located overseas.

In a bulletin to private industry last week, the FBI and Department and Homeland Security said, “We do not currently have specific intelligence reflecting additional attack planning against the United States stemming from the Hamas attacks in Israel which began on October 7,” but warned the public to remain vigilant and report suspicious activity to law enforcement, noting, “In recent years, there have been several events and incidents in the United States that were purportedly motivated, at least in part, by the conflict between Israel and Hamas.”

Of particular concern to public safety personnel is the “lone wolf” threat, one of the sources said Tuesday, a reference to an individual who may become radicalized to conduct violence but not part of a formal extremist group.

“A group of terrorists communicating with each other provides various avenues for possible exploitation using our surveillance capabilities,” the source said, but noted the more difficult task of detecting a lone individual who may not telegraph their attack plans to anyone.

While federal, state, and local authorities work behind the scenes to detect potential threats, police departments across the country continue to maintain visible enforcement postures in and around possible targets.

In Los Angeles, for example, the Los Angeles Police Department has adjusted patrol patterns to include frequent visibility around certain houses of worship and maintains continual outreach to the Jewish and Muslim communities, a law enforcement source told CNN Wednesday.

In addition to officers on the beat, LAPD’s Counter-Terrorism and Special Operations Bureau continues to monitor developments in the Middle East and the potential for events abroad to inspire violence at home, the source said.

US embassies, consulates put on alert

Officials have also urged caution to US citizens and diplomats abroad.

On Thursday, the State Department advised Americans worldwide “to exercise increased caution” due to “increased tensions in various locations around the world, the potential for terrorist attacks, (and) demonstrations or violent actions against U.S. citizens and interests.”

Citizens abroad were advised to “stay alert in locations frequented by tourists” and to enroll in the State Department’s Smart Traveler Enrollment Program “to receive information and alerts and make it easier to locate you in an emergency overseas.”

A day earlier, Secretary of State Antony Blinken sent a State Department cable to all US embassies and consulates across the world, ordering diplomatic security officers to convene each embassies’ security committee to conduct emergency reviews in an effort to determine if security needs to be ramped up.

Blinken’s cable – obtained by CNN – ordered the State Department’s Regional Security Officers, or RSOs, to consider whether messages to Americans in those countries are needed advising of potential areas to avoid or precautions to take. All embassies were directed to report back to the State Department in Washington on whatever steps were being taken.

CNN has reached out for comment to the State Department.

The State Department has already taken steps at numerous consulates and embassies in the region, as protests crop up throughout the Middle East and North Africa.

The US consulate in Adana, Turkey, for example, “will remain closed to the public until further notice” amid ongoing protests, and the US embassy in Beirut advised Americans to avoid the Awkar area – also due to demonstrations.

In the past week, the State Department has raised the travel advisory to the highest level for Israel and Lebanon to warn Americans not to travel there and has authorized the departure of some non-emergency US government personnel and family members from those countries.

CNN’s Jennifer Hansler contributed to this report.