The US National Counterterrorism Center (NCTC) warned on Friday that al Qaeda still poses a strong threat to the country.
The group and its Yemen-based branch, AQAP, are using online messages and global conflicts to inspire attacks, the NCTC said in a memo to law enforcement.
Officials urged government workers to keep travel plans private, avoid posting schedules online, and remove badges or ID when off duty.
The memo also warned that large gatherings such as sports games or music concerts could be targets. It advised police to increase their presence and hold security briefings before such events.
Al Qaeda carried out the September 11, 2001 attacks in New York and Washington, killing nearly 3,000 people. The US lists it as a foreign terrorist organization.
The Department of Homeland Security earlier reported that al Qaeda continues to plan attacks and is trying to reach Western audiences.
The NCTC said sharing these warnings will help law enforcement stop threats and protect the public.
