The United States issued a worldwide travel alert on Monday, warning its citizens of "increased terrorist threats" after the Paris attacks.
"Current information suggests that ISIL (Islamic State), al-Qaida, Boko Haram, and other terrorist groups continue to plan terrorist attacks in multiple regions," the State Department said, adding that possible attacks "may employ a wide variety of tactics, using conventional and non-conventional weapons."
"U.S. citizens should exercise vigilance when in public places or using transportation," it said in a warning posted on its website. "Be aware of immediate surroundings and avoid large crowds or crowed places," and especially be alerted during holiday times, it said.
The travel alert will expire on February 24, 2016, it said.
The Islamic State (IS), a militant group that has overrun vast swaths of territory in Iraq and Syria, claimed responsibility for the bloody Paris carnage earlier this month, which killed at least 129 people and injured hundreds of others.
IS militants threatened to bomb the White House and launch more attacks in Paris, according to a recent video.
However, FBI Director James Comey said last week that these videos are just a kind of propaganda, "not credible intelligence."
