The FBI has issued an alert to police warning anarchists dressed in Halloween costumes plan to create disturbances and attack responding police.

The "Halloween Revolt," according to the federal law enforcement agency, is planned by the National Liberation Militia, a group reportedly from Eugene, Oregon, and said to be responsible for violence in Seattle during the World Trade Organization conference in 1999.

According to the New York Post the group is calling for members to wear Halloween masks and use weapons such as bricks, bottles and firearms.

In his film Police State 2, Alex Jones showed how the police in Seattle allowed black bloc anarchists to stage a riot in downtown Seattle while they concentrated on preventing the movement of peaceful protestors. The film presents evidence that anarchist groups are actually controlled by the state and used to demonize peaceful protesters.

In 2007 during the Security and Prosperity Partnership summit in Montebello, Canada, police were exposedacting as anarchists and caught trying to incite violence and rioting.

Denver cops were found to have used undercover detectives to instigate violence against police during the 2008 Democratic National Convention andduring the G20 in Pittsburgh provocateurs were used to stir up trouble.

Black Bloc anarchists were also used to disrupt anddiscredit the Occupy movement.

The FBI warning follows remarks made by FBI director James Comey. He said the "Ferguson Effect," criminals emboldened by criticism of police following the shooting of Michael Brown in Missouri, has resulted in higher crime rates.