The Suffolk and Nassau police departments said they're taking precautions following the execution-style slaying of two NYPD officers on Saturday.
All Suffolk police officers were instructed "to maintain a heightened level of awareness," though there are no specific credible threats, police said in a statement.
Nassau police said the department is "taking appropriate precautions," a spokesman said.
Two NYPD officers were shot to death while sitting in their patrol car in Brooklyn on Saturday afternoon by a gunman who had vowed online hours earlier to kill cops.
The gunman, Ismaaiyl Brinsley, 28, traveled to New York to carry out his plot after shooting his ex-girlfriend near Baltimore. His online postings said he was avenging the controversial deaths of two black men at police hands in Ferguson, Missouri, and Staten Island.
The officers, Wenjian Liu, 32, and Rafael Ramos, 40, were shot at point-blank range in the ambush attack near the intersection of Myrtle and Tompkins avenues in Brooklyn's Bedford-Stuyvesant section at 2:47 p.m., police said.
The killings happened just as the NYPD received word from police in Baltimore County, Maryland, that Brinsley had shot his former girlfriend and might be on his way to New York to harm police.
"Two of New York's finest were shot and killed with no warning, no provocation," NYPD Commissioner William Bratton said during a news conference Saturday night at Woodhull Medical Center, where both officers were pronounced dead. "They were quite simply assassinated, targeted for their uniform and for the responsibility they embraced to keep the people of the city safe."