The US has issued a rare global travel alert to its citizens about the threat of a terrorist attack, citing Sydney’s “lone-wolf attack” in which two people died after a gunman held 17 people hostage in a city café and is only the second of its kind. It said US citizens “should be extra cautious, maintain a very high level of vigilance and take appropriate steps to ehance their personal security” over the holiday period. Sent out by the State Department, the warning added analysis of past attacks and threat reporting “strongly suggests” a focus by terrorists to strike against public venues, churches, schools “among other targets”, not just US government facilities.

“We strongly recommend that US citizens traveling abroad enroll in the Department of State’s Smart Traveler Enrollment Program (STEP) [sic].” The alert was set to expire on March 19. The only other time the US has issued a global travel alert was in August 2013. At that point the alert, which expired at the end of that month, suggested al Qaeda militants or its allies could target either US government or private American interests. The New York Times reported officials had intercepted electronic communications among senior operates of al Qaeda. Late this week, London’s top policeman said Britain had thwarted a Sydney-style “lone wolf” attack just days before it was meant to happen, adding his force had foiled five terror plots in the last four months alone. Britain raised it terrorism alert to the second-highest level in August and last month said it was facing the biggest terrorism threat in its history because of radicalised Britons returning from fighting in Syria and Iraq. “They’ve been very close to going and hurting somebody, badly, or killing them … within days,” London’s police chief, Bernard Hogan-Howe, said in an interview on LBC Radio on Wednesday, local time. “In terms of plots over this last four months really it’s probably five. And we’ve arrested I think it’s about 35 people.” Hogan-Howe said the activity had put a strain on resources and that more funding was needed to address backlogs in retrieving digital evidence to identify such plots.