WASHINGTON — The Federal Bureau of Investigation has instructed agents to interrogate suspected “operational terrorists” about immediate threats to public safety without advising them of their Miranda rights to remain silent and to have an attorney present.

A three-page F.B.I. memorandum, dated Oct. 21, 2010, also encouraged agents to use a broad interpretation of public safety-related questions. It said that the “magnitude and complexity” of the terrorist threat justified “a significantly more extensive public safety interrogation without Miranda warnings than would be permissible in an ordinary criminal case.”

“Depending on the facts, such interrogation might include, for example, questions about possible impending or coordinated terrorist attacks; the location, nature and threat posed by weapons that might post an imminent danger to the public; and the identities, locations, and activities or intentions of accomplices who may be plotting additional imminent attacks,” the memo said.

In the Miranda case, the Supreme Court ruled that if prosecutors want to use statements made by the defendant while in custody against him, police must have warned him of his rights before those statements were made. The court later created an exception for answers to questions about immediate threats to public safety.