The US Department of State has issued a rare worldwide travel alert for American citizens in response to “increased terrorist threats”.

It said “current information” suggested ISIS, al-Qaeda, Boko Haram and others continued “to plan terrorist attacks in multiple regions”.

The alert, the state department said, will remain in place until February 24, 2016.

Russia, France, Mali and several other countries have seen deadly attacks in the past month.

The alert advises US citizens to “exercise vigilance when in public places or using transportation”.

US citizens are also advised to “be aware of immediate surroundings and avoid large crowds or crowded places”.