The U.S. Department of State issued a worldwide travel alert Monday, citing information that suggests terrorist groups are planning attacks in multiple regions.

Authorities believe the likelihood of terror attacks, like deadliest attacks in Paris since World War II that unfolded earlier this month, will continue as members of ISIL/Da’esh return from Syria and Iraq. There is a continuing threat from independent people planning attacks that are inspired by major terrorist organizations but conducted on an individual basis.

Such attacks, according to authorities, could involve the targeting of both official and private interests.

There have been multiple attacks in France, Nigeria, Denmark, Turkey and Mali in the past year, and ISIL has claimed responsibility for the bombing of a Russian plane in Egypt last month.

U.S. citizens are urged to remain aware of surroundings and exercise particular caution during the holiday season, and at holiday festivals and events.

Travel alerts are issued during short-term events like outbreaks or an elevated risk of terrorist attacks.