"Current information suggests that ISIL (also known as the Islamic State of Iraq and Syria), Al Qaeda, Boko Haram, and other terrorist groups continue to plan terrorist attacks in multiple regions," the State Department said in its latest travel advisory issued on Monday.
Noting that these attacks may employ a wide variety of tactics using conventional and non-conventional weapons and could target both official and private interests, the State Department said authorities believe the likelihood of terror attacks will continue as members of ISIL 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," the State Department said.
Extremists have targeted large sporting events, theatres, open markets and aviation services.
In the past year, there have been multiple attacks in France, Nigeria, Denmark, Turkey, and Mali.
The Islamic State has claimed responsibility for the bombing of a Russian airliner in Egypt, it said.
As such, US citizens should exercise vigilance when in public places or using transportation, the State Department said.
"Be aware of immediate surroundings and avoid large crowds or crowed places. Exercise particular caution during the holiday season and at holiday festivals or events. US citizens should monitor media and local information sources and factor updated information into personal travel plans and activities," it said.
The alert, which expires on February 24, comes as a massive manhunt is underway in France and Belgium for Belgian-born Salah Abdeslam, suspected of playing a role in the horrific shooting and suicide bombings in Paris in which 130 people were killed.
The Islamic State terror group had claimed reponsibility for the attacks.
Following the Paris attacks, armed gunmen stormed a luxury hotel in Mali last week and took hostages in which 19 people lost their lives. An al-Qaeda affiliate group has claimed responsibility for the attack.