U.S. federal officials are telling police to be vigilant on the anniversary of the Sept. 11 attacks, though they say it is routine advice.

Friday is the eighth anniversary of the hijacked jetliner crashes that killed nearly 3,000 people in the U.S.

The FBI and Homeland Security Department sent a bulletin to law enforcement agencies nationwide Thursday evening, a copy of which was reviewed by The Associated Press. The bulletin is similar to past advisories on holidays and other significant dates, and gives no indication of any specific threat.

It reminds police that terrorists in other countries recently have attacked public business sites like hotels.

Justice Department spokesman Richard Kolko said issuing the bulletin is routine.