The United States yesterday issued a worldwide alert for Americans planning to travel, citing the "increased terrorist threats".
The State Department did not go as far as to advise people against travel, but said US citizens should be vigilant, especially in crowded places.
"Current information suggests that (Islamic State), al-Qaeda, Boko Haram, and other terrorist groups continue to plan terrorist attacks in multiple regions," it said.
"Authorities believe the likelihood of terror attacks will continue as members of (Islamic State) return from Syria and Iraq."
"Additionally, there is a continuing threat from unaffiliated persons planning attacks inspired by major terrorist organisations but conducted on an individual basis."
It will remain in place until 24 February.
The country has regularly issued such global travel alerts since the September 11 attacks in 2001, and a state department official said the latest alert, which expires February 24, essentially updates past warnings.
The travel alert comes in the wake of deadly terror attacks carried out by militants in France and Mali. France has been under a state of emergency since the attacks, while Belgian capital Brussels has been on lockdown for the past few days over fears of an "imminent" Paris-style attack.