The FBI and Department of Homeland Security issued a bulletin Friday warning of potential attacks against law enforcement officers and the military during the July 4th holiday, CBS News has learned.

The bulletin is not related to Friday's attacks in France, Tunisia and Kuwait.

However, Homeland Security Secretary Jeh Johnson says his department is encouraging law enforcement "to be vigilant and prepared" ahead of the holiday in the U.S. following those three attacks.

Johnson says people should attend Independence Day events as planned but "remain vigilant" and report any suspicious activity.

He says U.S. authorities will adjust security measures, including those unseen by the public, as necessary.

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A gunman killed at least 37 people and wounded 36 in an attack on a beach resort in Tunisia Friday. In Kuwait, a suicide bomber killed at least 25 people, while a man with suspected ties to French Islamic radicals rammed a car into a gas factory in southeastern France, triggering an explosion that injured two people. The severed head of a local businessman was left hanging at the factory's entrance.