Riot police
Riot policeReuters

Law enforcement officials are concerned about possible violence by anarchist extremists at the upcoming Republican and Democratic national conventions, according to an intelligence bulletin prepared by the FBI and Department of Homeland Security.

The bulletin, which was obtained by CNN, states the FBI has intelligence indicating that individuals from New York "planned to travel to Tampa and attempt to close" all of the Tampa Bay-area bridges during the Republican National Convention next week.

According to the document, the FBI's information, which had been obtained in March, showed that anarchist extremists proposed "engaging in potentially destructive criminal activities against critical infrastructure outside the security perimeter throughout the Tampa Bay region because they expected access to the main RNC venue to be tightly controlled."

The FBI routinely issues intelligence bulletins in advance of many major events to warn local law enforcement of possible security concerns, CNN reported.

The document notes anarchists have a history of attempting to disrupt major events.

"During past national and international political and economic events, anarchist extremists have blocked streets, intersections, and bridges to disrupt or impede local business operations and public transportation access and, in some instances have initiated violent confrontations with police," the document states.

According to the law enforcement alert, the "FBI and DHS assess with high confidence anarchist extremists will target similar infrastructure in Tampa and Charlotte, with potentially significant impacts on public safety and transportation."

The bulletin states that while law enforcement agencies believe most protesters at the conventions will obey laws, anarchists would be the most likely exceptions, CNN reported. 

The notice warned that state and local law enforcement agencies should be on the lookout for anarchists acquiring materials that could be used to make improvised explosive devices, obtaining firearms training and preparing for violence with groups they oppose, such as white supremacists.