The US department of state has issued a global travel warning, following a spate of terror attacks in Canada, Australia and most recently France.
In a statement posted online, it said that the recent attacks served as a reminder to “maintain a high level of vigilance” and “take apropriate steps to increase security awareness.
It added that it remains “concerned about the continued threat of terrorist attacks, demonstrations, and other violent actions against US citizens and interests overseas”.
In particular it noted the “high degree of sophistication and advance weapons handling” employed by the terrorists, and said their confidence was indicative of prior training.
On Wednesday, two brothers named Saif and Cherif Kouachi launched an attack on the offices of the satirical magazine Charlie Hebdo in Paris, in which 12 people were killed.
This was followed by an attack by on a kosher supermarket in the French capital.The attacker killed four hostages and said his motive was to “target Jews”.
Last month, hostages were held at a cafe in Sydney, Australia, and in October a soldier was killed near Canada's parliament.
Areas listed as potentially dangerous include Europe, the Middle East, Africa, south Asia and Central Asia. The warning also cites the US-led intervention against the Islamic State (IS) in Syria and Iraq as a cause of possible retaliation.