A student walks through Harvard Yard at Harvard University in Cambridge, Massachusetts, in this file photo taken November 16, 2012. Harvard University said on its website on Monday that it had received an "unconfirmed" bomb threat and was evacuating four buildings on its campus outside Boston. [Photo/Agencies]

WASHINGTON - Harvard University said on Monday it had received "unconfirmed" bomb threat which prompted the university to evacuate four buildings on its campus.

"We received an unconfirmed bomb threat affecting the Science Center, as well as Sever, Emerson and Thayer Halls on the Cambridge campus," the university said on its website.

A warning was first posted on its official website at 12:31 p.m. local time and university authorities said all the four buildings had been evacuated and law enforcement officials were on scene.

The news of a possible bomb threat came just hours after the director of the Central Intelligence Agency (CIA) John Brennan warned that more attacks may occur following Friday's deadly assault allegedly by the Islamic State (IS) militants across the French capital.

Reports also emerged on Monday of a new video by the extremist group, which claimed that it planned to "strike America at its center in Washington" and that other countries who had participated in counter-IS strikes would also be the group's targets.

According to the US TV network CNN, a spokesperson for the Federal Bureau of Investigation said on Monday in response to the video that "at this time, there is no specific or credible threat to the United States."

So far, it remained unclear whether the unconfirmed bomb threat received by Harvard was related to the IS video.