Homeland Security Secretary Jeh Johnson said his department is encouraging law enforcement "to be vigilant and prepared" ahead of the July 4th holiday in the U.S. following attacks in France, Tunisia and Kuwait.
Johnson said people should attend Independence Day events as planned but "remain vigilant" and report any suspicious activity.
He said U.S. authorities will adjust security measures, including those unseen by the public, as necessary.
A gunman killed at least 37 people and wounded 36 in an attack on a beach resort in Tunisia on 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.