The State Department is warning Americans traveling abroad to be extra cautious over the holidays.

In a worldwide travel alert issued Friday, the department says an attack this week in Australia highlights the need to be vigilant. The alert says U.S. citizens traveling abroad should be mindful that terrorist groups, or those inspired by them, can pose unpredictable threats in public venues.

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

A gunman in Sydney took 17 people hostage at a café on Monday. The siege ended 16 hours later in a barrage of gunfire that left two hostages and the Iranian-born gunman dead.

The travel alert lasts into March.