The State Department is warning United States citizens travelling abroad to be extra cautious over the holidays.

In a worldwide travel alert issued on Friday, the department said an attack this week in Australia highlights the need to be vigilant.

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The alert said US citizens travelling abroad should be mindful that terrorist groups, or those inspired by them, can pose unpredictable threats in public venues.

The alert said an analysis of past attacks and threat reporting strongly suggests that terrorists are focused on hotels, shopping areas, places of worship and schools.

The travel alert lasts into March.