WASHINGTON - The US State Department on Thursday urged US citizens to exercise caution while traveling during the Christmas and New Year holiday season.

"As we approach the holidays, the US Department of State reminds US citizens of our Worldwide Travel Alert issued on November 23, and the continuing need to exercise caution during the holiday season," the Department said in a news release.

In the Nov. 23 global travel alert, the State Department "alerts US citizens to possible risks of travel due to increased terrorist threats."

Citing "current information," it said various terror groups including the extremist groups the Islamic State (IS), al-Qaida, and Boko Haram "continue to plan terrorist attacks in multiple regions."

"These attacks may employ a wide variety of tactics, using conventional and non-conventional weapons and targeting both official and private interests," said the alert notice which will expire on Feb. 24, 2016.

It said that the likelihood of terror attacks would continue as members of IS return from Syria and Iraq, while there is a continuing threat from unaffiliated persons planning attacks inspired by major terror groups.

Extremists have targeted large sporting events, theaters, open markets, and aviation services, it said.

It urged US citizens to "exercise vigilance" when in public places or using transportation, and avoid large crowds or crowded places.

The November alert was issued after the Nov. 13 massive terror attacks in Paris, France, in which IS terrorists killed 130 people and wounded 350 others in a series of well-coordinated attacks.

On Dec. 2, Syed Rizwan Farook and Tashfeen Malik, a US couple armed with assault weapons, opened fire at a social services center in San Bernardino, California, killing 14 people and injuring 21 others. The couple were believed to have been radicalized by IS.